[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The appendfile
transport delivers a message by appending it to an existing
file, or by creating an entirely new file in a specified directory. Single
files to which messages are appended can be in the traditional Unix mailbox
format, or optionally in the MBX format supported by the Pine MUA and
University of Washington IMAP daemon, inter alia. When each message is
being delivered as a separate file, "maildir" format can optionally be used
to give added protection against failures that happen part-way through the
delivery. A third form of separate-file delivery known as "mailstore" is also
supported. For all file formats, Exim attempts to create as many levels of
directory as necessary, provided that create_directory
is set.
The code for the optional formats is not included in the Exim binary by default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or SUPPORT_MAILSTORE in ‘Local/Makefile’ to have the appropriate code included.
Exim recognizes system quota errors, and generates an appropriate message. Exim also supports its own quota control within the transport, for use when the system facility is unavailable or cannot be used for some reason.
If there is an error while appending to a file (for example, quota exceeded or partition filled), Exim attempts to reset the file’s length and last modification time back to what they were before. If there is an error while creating an entirely new file, the new file is removed.
Before appending to a file, a number of security checks are made, and the file is locked. A detailed description is given below, after the list of private options.
The appendfile
transport is most commonly used for local deliveries to
users’ mailboxes. However, it can also be used as a pseudo-remote transport for
putting messages into files for remote delivery by some means other than Exim.
"Batch SMTP" format is often used in this case (see the use_bsmtp
option).
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The file
option specifies a single file, to which the message is appended;
the directory
option specifies a directory, in which a new file containing
the message is created. Only one of these two options can be set, and for
normal deliveries to mailboxes, one of them must be set.
However, appendfile
is also used for delivering messages to files or
directories whose names (or parts of names) are obtained from alias,
forwarding, or filtering operations (for example, a save
command in a
user’s Exim filter). When such a transport is running, $local_part
contains
the local part that was aliased or forwarded, and $address_file
contains the
name (or partial name) of the file or directory generated by the redirection
operation. There are two cases:
file
nor directory
is set, the redirection operation
must specify an absolute path (one that begins with ‘/’). This is the most
common case when users with local accounts use filtering to sort mail into
different folders. See for example, the address_file
transport in the
default configuration. If the path ends with a slash, it is assumed to be the
name of a directory. A delivery to a directory can also be forced by setting
maildir_format
or mailstore_format
.
file
or directory
is set for a delivery from a redirection, it is
used to determine the file or directory name for the delivery. Normally, the
contents of $address_file
are used in some way in the string expansion.
As an example of the second case, consider an environment where users do not have home directories. They may be permitted to use Exim filter commands of the form:
save folder23 |
or Sieve filter commands of the form:
require "fileinto"; fileinto "folder23"; |
In this situation, the expansion of file
or directory
in the transport
must transform the relative path into an appropriate absolute file name. In the
case of Sieve filters, the name inbox must be handled. It is the name that
is used as a result of a "keep" action in the filter. This example shows one
way of handling this requirement:
file = ${if eq{$address_file}{inbox} \ {/var/mail/$local_part} \ {${if eq{${substr_0_1:$address_file}}{/} \ {$address_file} \ {$home/mail/$address_file} \ }} \ } |
With this setting of file
, inbox refers to the standard mailbox
location, absolute paths are used without change, and other folders are in the
‘mail’ directory within the home directory.
Note 1: While processing an Exim filter, a relative path such as
‘folder23’ is turned into an absolute path if a home directory is known to
the router. In particular, this is the case if check_local_user
is set. If
you want to prevent this happening at routing time, you can set
router_home_directory
empty. This forces the router to pass the relative
path to the transport.
Note 2: An absolute path in $address_file
is not treated specially;
the file
or directory
option is still used if it is set.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
allow_fifo | Use: appendfile | Type: boolean | Default: false |
Setting this option permits delivery to named pipes (FIFOs) as well as to regular files. If no process is reading the named pipe at delivery time, the delivery is deferred.
allow_symlink | Use: appendfile | Type: boolean | Default: false |
By default, appendfile
will not deliver if the path name for the file is
that of a symbolic link. Setting this option relaxes that constraint, but there
are security issues involved in the use of symbolic links. Be sure you know
what you are doing if you set this. Details of exactly what this option affects
are included in the discussion which follows this list of options.
batch_id | Use: appendfile | Type: string* | Default: unset |
See the description of local delivery batching in chapter Address batching in local transports.
However, batching is automatically disabled for appendfile
deliveries that
happen as a result of forwarding or aliasing or other redirection directly to a
file.
batch_max | Use: appendfile | Type: integer | Default: 1 |
See the description of local delivery batching in chapter Address batching in local transports.
check_group | Use: appendfile | Type: boolean | Default: false |
When this option is set, the group owner of the file defined by the file
option is checked to see that it is the same as the group under which the
delivery process is running. The default setting is false because the default
file mode is 0600, which means that the group is irrelevant.
check_owner | Use: appendfile | Type: boolean | Default: true |
When this option is set, the owner of the file defined by the file
option
is checked to ensure that it is the same as the user under which the delivery
process is running.
check_string | Use: appendfile | Type: string | Default: see below |
As appendfile
writes the message, the start of each line is tested for
matching check_string
, and if it does, the initial matching characters are
replaced by the contents of escape_string
. The value of check_string
is
a literal string, not a regular expression, and the case of any letters it
contains is significant.
If use_bsmtp
is set the values of check_string
and escape_string
are forced to "." and ".." respectively, and any settings in the
configuration are ignored. Otherwise, they default to "From" and
">From" when the file
option is set, and unset when any of the
directory
, maildir
, or mailstore
options are set.
The default settings, along with message_prefix
and message_suffix
, are
suitable for traditional "BSD" mailboxes, where a line beginning with
"From" indicates the start of a new message. All four options need changing
if another format is used. For example, to deliver to mailboxes in MMDF format:
check_string = "\1\1\1\1\n" escape_string = "\1\1\1\1 \n" message_prefix = "\1\1\1\1\n" message_suffix = "\1\1\1\1\n" |
create_directory | Use: appendfile | Type: boolean | Default: true |
When this option is true, Exim attempts to create any missing superior
directories for the file that it is about to write. A created directory’s mode
is given by the directory_mode
option.
The group ownership of a newly created directory is highly dependent on the operating system (and possibly the file system) that is being used. For example, in Solaris, if the parent directory has the setgid bit set, its group is propagated to the child; if not, the currently set group is used. However, in FreeBSD, the parent’s group is always used.
create_file | Use: appendfile | Type: string | Default: anywhere |
This option constrains the location of files and directories that are created
by this transport. It applies to files defined by the file
option and
directories defined by the directory
option. In the case of maildir
delivery, it applies to the top level directory, not the maildir directories
beneath.
The option must be set to one of the words "anywhere", "inhome", or
"belowhome". In the second and third cases, a home directory must have been
set for the transport. This option is not useful when an explicit file name is
given for normal mailbox deliveries. It is intended for the case when file
names are generated from users’ ‘.forward’ files. These are usually handled
by an appendfile
transport called address_file
. See also
file_must_exist
.
directory | Use: appendfile | Type: string* | Default: unset |
This option is mutually exclusive with the file
option, but one of file
or directory
must be set, unless the delivery is the direct result of a
redirection (see section The file and directory options).
When directory
is set, the string is expanded, and the message is delivered
into a new file or files in or below the given directory, instead of being
appended to a single mailbox file. A number of different formats are provided
(see maildir_format
and mailstore_format
), and see section
Operational details for delivery to a new file for further details of this form of delivery.
directory_file | Use: appendfile | Type: string* | Default: see below |
When directory
is set, but neither maildir_format
nor
mailstore_format
is set, appendfile
delivers each message into a file
whose name is obtained by expanding this string. The default value is:
q${base62:$tod_epoch}-$inode |
This generates a unique name from the current time, in base 62 form, and the
inode of the file. The variable $inode
is available only when expanding this
option.
directory_mode | Use: appendfile | Type: octal integer | Default: 0700 |
If appendfile
creates any directories as a result of the
create_directory
option, their mode is specified by this option.
escape_string | Use: appendfile | Type: string | Default: see description |
See check_string
above.
file | Use: appendfile | Type: string* | Default: unset |
This option is mutually exclusive with the directory
option, but one of
file
or directory
must be set, unless the delivery is the direct result
of a redirection (see section The file and directory options). The file
option
specifies a single file, to which the message is appended. One or more of
use_fcntl_lock
, use_flock_lock
, or use_lockfile
must be set with
file
.
If you are using more than one host to deliver over NFS into the same mailboxes, you should always use lock files.
The string value is expanded for each delivery, and must yield an absolute path. The most common settings of this option are variations on one of these examples:
file = /var/spool/mail/$local_part file = /home/$local_part/inbox file = $home/inbox |
In the first example, all deliveries are done into the same directory. If Exim
is configured to use lock files (see use_lockfile
below) it must be able to
create a file in the directory, so the "sticky" bit must be turned on for
deliveries to be possible, or alternatively the group
option can be used to
run the delivery under a group id which has write access to the directory.
file_format | Use: appendfile | Type: string | Default: unset |
This option requests the transport to check the format of an existing file
before adding to it. The check consists of matching a specific string at the
start of the file. The value of the option consists of an even number of
colon-separated strings. The first of each pair is the test string, and the
second is the name of a transport. If the transport associated with a matched
string is not the current transport, control is passed over to the other
transport. For example, suppose the standard local_delivery
transport has
this added to it:
file_format = "From : local_delivery :\ \1\1\1\1\n : local_mmdf_delivery" |
Mailboxes that begin with "From" are still handled by this transport, but if
a mailbox begins with four binary ones followed by a newline, control is passed
to a transport called local_mmdf_delivery
, which presumably is configured
to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
is assumed to match the current transport. If the start of a mailbox doesn’t
match any string, or if the transport named for a given string is not defined,
delivery is deferred.
file_must_exist | Use: appendfile | Type: boolean | Default: false |
If this option is true, the file specified by the file
option must exist.
A temporary error occurs if it does not, causing delivery to be deferred.
If this option is false, the file is created if it does not exist.
lock_fcntl_timeout | Use: appendfile | Type: time | Default: 0s |
By default, the appendfile
transport uses non-blocking calls to fcntl()
when locking an open mailbox file. If the call fails, the delivery process
sleeps for lock_interval
and tries again, up to lock_retries
times.
Non-blocking calls are used so that the file is not kept open during the wait
for the lock; the reason for this is to make it as safe as possible for
deliveries over NFS in the case when processes might be accessing an NFS
mailbox without using a lock file. This should not be done, but
misunderstandings and hence misconfigurations are not unknown.
On a busy system, however, the performance of a non-blocking lock approach is not as good as using a blocking lock with a timeout. In this case, the waiting is done inside the system call, and Exim’s delivery process acquires the lock and can proceed as soon as the previous lock holder releases it.
If lock_fcntl_timeout
is set to a non-zero time, blocking locks, with that
timeout, are used. There may still be some retrying: the maximum number of
retries is
(lock_retries * lock_interval) / lock_fcntl_timeout |
rounded up to the next whole number. In other words, the total time during
which appendfile
is trying to get a lock is roughly the same, unless
lock_fcntl_timeout
is set very large.
You should consider setting this option if you are getting a lot of delayed local deliveries because of errors of the form
failed to lock mailbox /some/file (fcntl) |
lock_flock_timeout | Use: appendfile | Type: time | Default: 0s |
This timeout applies to file locking when using flock()
(see
use_flock
); the timeout operates in a similar manner to
lock_fcntl_timeout
.
lock_interval | Use: appendfile | Type: time | Default: 3s |
This specifies the time to wait between attempts to lock the file. See below for details of locking.
lock_retries | Use: appendfile | Type: integer | Default: 10 |
This specifies the maximum number of attempts to lock the file. A value of zero is treated as 1. See below for details of locking.
lockfile_mode | Use: appendfile | Type: octal integer | Default: 0600 |
This specifies the mode of the created lock file, when a lock file is being
used (see use_lockfile
and use_mbx_lock
).
lockfile_timeout | Use: appendfile | Type: time | Default: 30m |
When a lock file is being used (see use_lockfile
), if a lock file already
exists and is older than this value, it is assumed to have been left behind by
accident, and Exim attempts to remove it.
mailbox_filecount | Use: appendfile | Type: string* | Default: unset |
If this option is set, it is expanded, and the result is taken as the current number of files in the mailbox. It must be a decimal number, optionally followed by K or M. This provides a way of obtaining this information from an external source that maintains the data.
mailbox_size | Use: appendfile | Type: string* | Default: unset |
If this option is set, it is expanded, and the result is taken as the current size the mailbox. It must be a decimal number, optionally followed by K or M. This provides a way of obtaining this information from an external source that maintains the data. This is likely to be helpful for maildir deliveries where it is computationally expensive to compute the size of a mailbox.
maildir_format | Use: appendfile | Type: boolean | Default: false |
If this option is set with the directory
option, the delivery is into a new
file, in the "maildir" format that is used by other mail software. When the
transport is activated directly from a redirect
router (for example, the
address_file
transport in the default configuration), setting
maildir_format
causes the path received from the router to be treated as a
directory, whether or not it ends with ‘/’. This option is available only if
SUPPORT_MAILDIR is present in ‘Local/Makefile’. See section
Maildir delivery below for further details.
maildir_quota_directory_regex | Use: appendfile | Type: string | Default: See below |
This option is relevant only when maildir_use_size_file
is set. It defines
a regular expression for specifying directories, relative to the quota
directory (see quota_directory
), that should be included in the quota
calculation. The default value is:
maildir_quota_directory_regex = ^(?:cur|new|\..*)$ |
This includes the ‘cur’ and ‘new’ directories, and any maildir++ folders (directories whose names begin with a dot). If you want to exclude the ‘Trash’ folder from the count (as some sites do), you need to change this setting to
maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$ |
This uses a negative lookahead in the regular expression to exclude the directory whose name is ‘.Trash’. When a directory is excluded from quota calculations, quota processing is bypassed for any messages that are delivered directly into that directory.
maildir_retries | Use: appendfile | Type: integer | Default: 10 |
This option specifies the number of times to retry when writing a file in "maildir" format. See section Maildir delivery below.
maildir_tag | Use: appendfile | Type: string* | Default: unset |
This option applies only to deliveries in maildir format, and is described in section Maildir delivery below.
maildir_use_size_file | Use: appendfile | Type: boolean | Default: false |
Setting this option true enables support for ‘maildirsize’ files. Exim
creates a ‘maildirsize’ file in a maildir if one does not exist, taking the
quota from the quota
option of the transport. If quota
is unset, the
value is zero. See maildir_quota_directory_regex
above and section
Maildir delivery below for further details.
maildirfolder_create_regex | Use: appendfile | Type: string | Default: unset |
The value of this option is a regular expression. If it is unset, it has no effect. Otherwise, before a maildir delivery takes place, the pattern is matched against the name of the maildir directory, that is, the directory containing the ‘new’ and ‘tmp’ subdirectories that will be used for the delivery. If there is a match, Exim checks for the existence of a file called ‘maildirfolder’ in the directory, and creates it if it does not exist. See section Maildir delivery for more details.
mailstore_format | Use: appendfile | Type: boolean | Default: false |
If this option is set with the directory
option, the delivery is into two
new files in "mailstore" format. The option is available only if
SUPPORT_MAILSTORE is present in ‘Local/Makefile’. See section Operational details for delivery to a new file
below for further details.
mailstore_prefix | Use: appendfile | Type: string* | Default: unset |
This option applies only to deliveries in mailstore format, and is described in section Operational details for delivery to a new file below.
mailstore_suffix | Use: appendfile | Type: string* | Default: unset |
This option applies only to deliveries in mailstore format, and is described in section Operational details for delivery to a new file below.
mbx_format | Use: appendfile | Type: boolean | Default: false |
This option is available only if Exim has been compiled with SUPPORT_MBX
set in ‘Local/Makefile’. If mbx_format
is set with the file
option,
the message is appended to the mailbox file in MBX format instead of
traditional Unix format. This format is supported by Pine4 and its associated
IMAP and POP daemons, by means of the c-client library that they all use.
Note: The message_prefix
and message_suffix
options are not
automatically changed by the use of mbx_format
. They should normally be set
empty when using MBX format, so this option almost always appears in this
combination:
mbx_format = true message_prefix = message_suffix = |
If none of the locking options are mentioned in the configuration,
use_mbx_lock
is assumed and the other locking options default to false. It
is possible to specify the other kinds of locking with mbx_format
, but
use_fcntl_lock
and use_mbx_lock
are mutually exclusive. MBX locking
interworks with c-client, providing for shared access to the mailbox. It
should not be used if any program that does not use this form of locking is
going to access the mailbox, nor should it be used if the mailbox file is NFS
mounted, because it works only when the mailbox is accessed from a single host.
If you set use_fcntl_lock
with an MBX-format mailbox, you cannot use
the standard version of c-client, because as long as it has a mailbox open
(this means for the whole of a Pine or IMAP session), Exim will not be able to
append messages to it.
message_prefix | Use: appendfile | Type: string* | Default: see below |
The string specified here is expanded and output at the start of every message.
The default is unset unless file
is specified and use_bsmtp
is not set,
in which case it is:
message_prefix = "From ${if def:return_path{$return_path}\ {MAILER-DAEMON}} $tod_bsdinbox\n" |
Note: If you set use_crlf
true, you must change any occurrences of
‘\n’ to ‘\r\n’ in message_prefix
.
message_suffix | Use: appendfile | Type: string* | Default: see below |
The string specified here is expanded and output at the end of every message.
The default is unset unless file
is specified and use_bsmtp
is not set,
in which case it is a single newline character. The suffix can be suppressed by
setting
message_suffix = |
Note: If you set use_crlf
true, you must change any occurrences of
‘\n’ to ‘\r\n’ in message_suffix
.
mode | Use: appendfile | Type: octal integer | Default: 0600 |
If the output file is created, it is given this mode. If it already exists and
has wider permissions, they are reduced to this mode. If it has narrower
permissions, an error occurs unless mode_fail_narrower
is false. However,
if the delivery is the result of a save
command in a filter file specifying
a particular mode, the mode of the output file is always forced to take that
value, and this option is ignored.
mode_fail_narrower | Use: appendfile | Type: boolean | Default: true |
This option applies in the case when an existing mailbox file has a narrower
mode than that specified by the mode
option. If mode_fail_narrower
is
true, the delivery is deferred ("mailbox has the wrong mode"); otherwise Exim
continues with the delivery attempt, using the existing mode of the file.
notify_comsat | Use: appendfile | Type: boolean | Default: false |
If this option is true, the comsat daemon is notified after every successful delivery to a user mailbox. This is the daemon that notifies logged on users about incoming mail.
quota | Use: appendfile | Type: string* | Default: unset |
This option imposes a limit on the size of the file to which Exim is appending,
or to the total space used in the directory tree when the directory
option
is set. In the latter case, computation of the space used is expensive, because
all the files in the directory (and any sub-directories) have to be
individually inspected and their sizes summed. (See quota_size_regex
and
maildir_use_size_file
for ways to avoid this in environments where users
have no shell access to their mailboxes).
As there is no interlock against two simultaneous deliveries into a multi-file mailbox, it is possible for the quota to be overrun in this case. For single-file mailboxes, of course, an interlock is a necessity.
A file’s size is taken as its used value. Because of blocking effects, this may be a lot less than the actual amount of disk space allocated to the file. If the sizes of a number of files are being added up, the rounding effect can become quite noticeable, especially on systems that have large block sizes. Nevertheless, it seems best to stick to the used figure, because this is the obvious value which users understand most easily.
The value of the option is expanded, and must then be a numerical value (decimal point allowed), optionally followed by one of the letters K, M, or G, for kilobytes, megabytes, or gigabytes. If Exim is running on a system with large file support (Linux and FreeBSD have this), mailboxes larger than 2G can be handled.
Note: A value of zero is interpreted as "no quota".
The expansion happens while Exim is running as root, before it changes uid for the delivery. This means that files that are inaccessible to the end user can be used to hold quota values that are looked up in the expansion. When delivery fails because this quota is exceeded, the handling of the error is as for system quota failures.
By default, Exim’s quota checking mimics system quotas, and restricts the
mailbox to the specified maximum size, though the value is not accurate to the
last byte, owing to separator lines and additional headers that may get added
during message delivery. When a mailbox is nearly full, large messages may get
refused even though small ones are accepted, because the size of the current
message is added to the quota when the check is made. This behaviour can be
changed by setting quota_is_inclusive
false. When this is done, the check
for exceeding the quota does not include the current message. Thus, deliveries
continue until the quota has been exceeded; thereafter, no further messages are
delivered. See also quota_warn_threshold
.
quota_directory | Use: appendfile | Type: string* | Default: unset |
This option defines the directory to check for quota purposes when delivering into individual files. The default is the delivery directory, or, if a file called ‘maildirfolder’ exists in a maildir directory, the parent of the delivery directory.
quota_filecount | Use: appendfile | Type: string* | Default: 0 |
This option applies when the directory
option is set. It limits the total
number of files in the directory (compare the inode limit in system quotas). It
can only be used if quota
is also set. The value is expanded; an expansion
failure causes delivery to be deferred. A value of zero is interpreted as
"no quota".
quota_is_inclusive | Use: appendfile | Type: boolean | Default: true |
See quota
above.
quota_size_regex | Use: appendfile | Type: string | Default: unset |
This option applies when one of the delivery modes that writes a separate file
for each message is being used. When Exim wants to find the size of one of
these files in order to test the quota, it first checks quota_size_regex
.
If this is set to a regular expression that matches the file name, and it
captures one string, that string is interpreted as a representation of the
file’s size. The value of quota_size_regex
is not expanded.
This feature is useful only when users have no shell access to their mailboxes
- otherwise they could defeat the quota simply by renaming the files. This
facility can be used with maildir deliveries, by setting maildir_tag
to add
the file length to the file name. For example:
maildir_tag = ,S=$message_size quota_size_regex = ,S=(\d+) |
An alternative to $message_size
is $message_linecount
, which contains the
number of lines in the message.
The regular expression should not assume that the length is at the end of the
file name (even though maildir_tag
puts it there) because maildir MUAs
sometimes add other information onto the ends of message file names.
quota_warn_message | Use: appendfile | Type: string* | Default: see below |
See below for the use of this option. If it is not set when
quota_warn_threshold
is set, it defaults to
quota_warn_message = "\ To: $local_part@$domain\n\ Subject: Your mailbox\n\n\ This message is automatically created \ by mail delivery software.\n\n\ The size of your mailbox has exceeded \ a warning threshold that is\n\ set by the system administrator.\n" |
quota_warn_threshold | Use: appendfile | Type: string* | Default: 0 |
This option is expanded in the same way as quota
(see above). If the
resulting value is greater than zero, and delivery of the message causes the
size of the file or total space in the directory tree to cross the given
threshold, a warning message is sent. If quota
is also set, the threshold
may be specified as a percentage of it by following the value with a percent
sign. For example:
quota = 10M quota_warn_threshold = 75% |
If quota
is not set, a setting of quota_warn_threshold
that ends with a
percent sign is ignored.
The warning message itself is specified by the quota_warn_message
option,
and it must start with a To: header line containing the recipient(s) of the
warning message. These do not necessarily have to include the recipient(s) of
the original message. A Subject: line should also normally be supplied. You
can include any other header lines that you want. If you do not include a
From: line, the default is:
From: Mail Delivery System <mailer-daemon@$qualify_domain_sender> |
If you supply a Reply-To: line, it overrides the global errors_reply_to
option.
The quota
option does not have to be set in order to use this option; they
are independent of one another except when the threshold is specified as a
percentage.
use_bsmtp | Use: appendfile | Type: boolean | Default: false |
If this option is set true, appendfile
writes messages in "batch SMTP"
format, with the envelope sender and recipient(s) included as SMTP commands. If
you want to include a leading HELO command with such messages, you can do
so by setting the message_prefix
option. See section Outgoing batched SMTP
for details of batch SMTP.
use_crlf | Use: appendfile | Type: boolean | Default: false |
This option causes lines to be terminated with the two-character CRLF sequence (carriage return, linefeed) instead of just a linefeed character. In the case of batched SMTP, the byte sequence written to the file is then an exact image of what would be sent down a real SMTP connection.
Note: The contents of the message_prefix
and message_suffix
options
(which are used to supply the traditional "From" and blank line separators
in Berkeley-style mailboxes) are written verbatim, so must contain their own
carriage return characters if these are needed. In cases where these options
have non-empty defaults, the values end with a single linefeed, so they must be
changed to end with ‘\r\n’ if use_crlf
is set.
use_fcntl_lock | Use: appendfile | Type: boolean | Default: see below |
This option controls the use of the fcntl()
function to lock a file for
exclusive use when a message is being appended. It is set by default unless
use_flock_lock
is set. Otherwise, it should be turned off only if you know
that all your MUAs use lock file locking. When both use_fcntl_lock
and
use_flock_lock
are unset, use_lockfile
must be set.
use_flock_lock | Use: appendfile | Type: boolean | Default: false |
This option is provided to support the use of flock()
for file locking, for
the few situations where it is needed. Most modern operating systems support
fcntl()
and lockf()
locking, and these two functions interwork with
each other. Exim uses fcntl()
locking by default.
This option is required only if you are using an operating system where
flock()
is used by programs that access mailboxes (typically MUAs), and
where flock()
does not correctly interwork with fcntl()
. You can use
both fcntl()
and flock()
locking simultaneously if you want.
Not all operating systems provide flock()
. Some versions of Solaris do not
have it (and some, I think, provide a not quite right version built on top of
lockf()
). If the OS does not have flock()
, Exim will be built without
the ability to use it, and any attempt to do so will cause a configuration
error.
Warning: flock()
locks do not work on NFS files (unless flock()
is just being mapped onto fcntl()
by the OS).
use_lockfile | Use: appendfile | Type: boolean | Default: see below |
If this option is turned off, Exim does not attempt to create a lock file when
appending to a mailbox file. In this situation, the only locking is by
fcntl()
. You should only turn use_lockfile
off if you are absolutely
sure that every MUA that is ever going to look at your users’ mailboxes uses
fcntl()
rather than a lock file, and even then only when you are not
delivering over NFS from more than one host.
In order to append to an NFS file safely from more than one host, it is
necessary to take out a lock before opening the file, and the lock file
achieves this. Otherwise, even with fcntl()
locking, there is a risk of
file corruption.
The use_lockfile
option is set by default unless use_mbx_lock
is set.
It is not possible to turn both use_lockfile
and use_fcntl_lock
off,
except when mbx_format
is set.
use_mbx_lock | Use: appendfile | Type: boolean | Default: see below |
This option is available only if Exim has been compiled with SUPPORT_MBX
set in ‘Local/Makefile’. Setting the option specifies that special MBX
locking rules be used. It is set by default if mbx_format
is set and none
of the locking options are mentioned in the configuration. The locking rules
are the same as are used by the c-client library that underlies Pine and
the IMAP4 and POP daemons that come with it (see the discussion below). The
rules allow for shared access to the mailbox. However, this kind of locking
does not work when the mailbox is NFS mounted.
You can set use_mbx_lock
with either (or both) of use_fcntl_lock
and
use_flock_lock
to control what kind of locking is used in implementing the
MBX locking rules. The default is to use fcntl()
if use_mbx_lock
is set
without use_fcntl_lock
or use_flock_lock
.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Before appending to a file, the following preparations are made:
create_directory
option is set. A created directory’s mode is given by the
directory_mode
option.
file_format
is set, the format of an existing file is checked. If this
indicates that a different transport should be used, control is passed to that
transport.
use_lockfile
is set, a lock file is built in a way that will work
reliably over NFS, as follows:
link()
succeeds, creation of the lock file has succeeded.
Unlink the hitching post name.
stat()
to get information about the hitching post file, and
then unlink hitching post name. If the number of links is exactly two, creation
of the lock file succeeded but something (for example, an NFS server crash and
restart) caused this fact not to be communicated to the link()
call.
lock_interval
and try again,
up to lock_retries
times. However, since any program that writes to a
mailbox should complete its task very quickly, it is reasonable to time out old
lock files that are normally the result of user agent and system crashes. If an
existing lock file is older than lockfile_timeout
Exim attempts to unlink
it before trying again.
lstat()
to discover whether the main file exists, and if
so, what its characteristics are. If lstat()
fails for any reason other
than non-existence, delivery is deferred.
allow_symlink
option is set, in which case the ownership of the link is
checked, and then stat()
is called to find out about the real file, which
is then subjected to the checks below. The check on the top-level link
ownership prevents one user creating a link for another’s mailbox in a sticky
directory, though allowing symbolic links in this case is definitely not a good
idea. If there is a chain of symbolic links, the intermediate ones are not
checked.
check_group
above) are
different from the user and group under which the delivery is running,
delivery is deferred.
mode_fail_narrower
is set false, in which case the delivery is tried using the existing
permissions.
appendfile
behaves as if it
hadn’t existed (see below). For any other failures, delivery is deferred.
file_must_exist
option is set. Otherwise, check that the file is being created in a permitted
directory if the create_file
option is set (deferring on failure), and then
open for writing as a new file, with the O_EXCL and O_CREAT options,
except when dealing with a symbolic link (the allow_symlink
option must be
set). In this case, which can happen if the link points to a non-existent file,
the file is opened for writing using O_CREAT but not O_EXCL, because
that prevents link following.
use_fcntl_lock
and use_flock_lock
are false, it is locked using fcntl()
or flock()
or both. If
use_mbx_lock
is false, an exclusive lock is requested in each case.
However, if use_mbx_lock
is true, Exim takes out a shared lock on the open
file, and an exclusive lock on the file whose name is
/tmp/.<device-number>.<inode-number> |
using the device and inode numbers of the open mailbox file, in accordance with
the MBX locking rules. This file is created with a mode that is specified by
the lockfile_mode
option.
If Exim fails to lock the file, there are two possible courses of action,
depending on the value of the locking timeout. This is obtained from
lock_fcntl_timeout
or lock_flock_timeout
, as appropriate.
If the timeout value is zero, the file is closed, Exim waits for
lock_interval
, and then goes back and re-opens the file as above and tries
to lock it again. This happens up to lock_retries
times, after which the
delivery is deferred.
If the timeout has a value greater than zero, blocking calls to fcntl()
or
flock()
are used (with the given timeout), so there has already been some
waiting involved by the time locking fails. Nevertheless, Exim does not give up
immediately. It retries up to
(lock_retries * lock_interval) / <timeout> |
times (rounded up).
At the end of delivery, Exim closes the file (which releases the fcntl()
and/or flock()
locks) and then deletes the lock file if one was created.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
When the directory
option is set instead of file
, each message is
delivered into a newly-created file or set of files. When appendfile
is
activated directly from a redirect
router, neither file
nor
directory
is normally set, because the path for delivery is supplied by the
router. (See for example, the address_file
transport in the default
configuration.) In this case, delivery is to a new file if either the path name
ends in ‘/’, or the maildir_format
or mailstore_format
option is set.
No locking is required while writing the message to a new file, so the various
locking options of the transport are ignored. The "From" line that by default
separates messages in a single file is not normally needed, nor is the escaping
of message lines that start with "From", and there is no need to ensure a
newline at the end of each message. Consequently, the default values for
check_string
, message_prefix
, and message_suffix
are all unset when
any of directory
, maildir_format
, or mailstore_format
is set.
If Exim is required to check a quota
setting, it adds up the sizes of all
the files in the delivery directory by default. However, you can specify a
different directory by setting quota_directory
. Also, for maildir
deliveries (see below) the ‘maildirfolder’ convention is honoured.
There are three different ways in which delivery to individual files can be
done, controlled by the settings of the maildir_format
and
mailstore_format
options. Note that code to support maildir or mailstore
formats is not included in the binary unless SUPPORT_MAILDIR or
SUPPORT_MAILSTORE, respectively, is set in ‘Local/Makefile’.
In all three cases an attempt is made to create the directory and any necessary
sub-directories if they do not exist, provided that the create_directory
option is set (the default). The location of a created directory can be
constrained by setting create_file
. A created directory’s mode is given by
the directory_mode
option. If creation fails, or if the
create_directory
option is not set when creation is required, delivery is
deferred.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
If the maildir_format
option is true, Exim delivers each message by writing
it to a file whose name is ‘tmp/<stime>.H<mtime>P<pid>.<host>’ in the
directory that is defined by the directory
option (the "delivery
directory"). If the delivery is successful, the file is renamed into the
‘new’ subdirectory.
In the file name, <stime> is the current time of day in seconds, and
<mtime> is the microsecond fraction of the time. After a maildir delivery,
Exim checks that the time-of-day clock has moved on by at least one microsecond
before terminating the delivery process. This guarantees uniqueness for the
file name. However, as a precaution, Exim calls stat()
for the file before
opening it. If any response other than ENOENT (does not exist) is given,
Exim waits 2 seconds and tries again, up to maildir_retries
times.
Before Exim carries out a maildir delivery, it ensures that subdirectories
called ‘new’, ‘cur’, and ‘tmp’ exist in the delivery directory. If they
do not exist, Exim tries to create them and any superior directories in their
path, subject to the create_directory
and create_file
options. If the
maildirfolder_create_regex
option is set, and the regular expression it
contains matches the delivery directory, Exim also ensures that a file called
‘maildirfolder’ exists in the delivery directory. If a missing directory or
‘maildirfolder’ file cannot be created, delivery is deferred.
These features make it possible to use Exim to create all the necessary files and directories in a maildir mailbox, including subdirectories for maildir++ folders. Consider this example:
maildir_format = true directory = /var/mail/$local_part\ ${if eq{$local_part_suffix}{}{}\ {/.${substr_1:$local_part_suffix}}} maildirfolder_create_regex = /\.[^/]+$ |
If $local_part_suffix
is empty (there was no suffix for the local part),
delivery is into a toplevel maildir with a name like ‘/var/mail/pimbo’ (for
the user called pimbo). The pattern in maildirfolder_create_regex
does
not match this name, so Exim will not look for or create the file
‘/var/mail/pimbo/maildirfolder’, though it will create
‘/var/mail/pimbo/{cur,new,tmp}’ if necessary.
However, if $local_part_suffix
contains ‘-eximusers’ (for example),
delivery is into the maildir++ folder ‘/var/mail/pimbo/.eximusers’, which
does match maildirfolder_create_regex
. In this case, Exim will create
‘/var/mail/pimbo/.eximusers/maildirfolder’ as well as the three maildir
directories ‘/var/mail/pimbo/.eximusers/{cur,new,tmp}’.
Warning: Take care when setting maildirfolder_create_regex
that it does
not inadvertently match the toplevel maildir directory, because a
‘maildirfolder’ file at top level would completely break quota calculations.
If Exim is required to check a quota
setting before a maildir delivery, and
quota_directory
is not set, it looks for a file called ‘maildirfolder’ in
the maildir directory (alongside ‘new’, ‘cur’, ‘tmp’). If this exists,
Exim assumes the directory is a maildir++ folder directory, which is one level
down from the user’s top level mailbox directory. This causes it to start at
the parent directory instead of the current directory when calculating the
amount of space used.
One problem with delivering into a multi-file mailbox is that it is
computationally expensive to compute the size of the mailbox for quota
checking. Various approaches have been taken to reduce the amount of work
needed. The next two sections describe two of them. A third alternative is to
use some external process for maintaining the size data, and use the expansion
of the mailbox_size
option as a way of importing it into Exim.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
If maildir_tag
is set, the string is expanded for each delivery.
When the maildir file is renamed into the ‘new’ sub-directory, the
tag is added to its name. However, if adding the tag takes the length of the
name to the point where the test stat()
call fails with ENAMETOOLONG,
the tag is dropped and the maildir file is created with no tag.
Tags can be used to encode the size of files in their names; see
quota_size_regex
above for an example. The expansion of maildir_tag
happens after the message has been written. The value of the $message_size
variable is set to the number of bytes actually written. If the expansion is
forced to fail, the tag is ignored, but a non-forced failure causes delivery to
be deferred. The expanded tag may contain any printing characters except "/".
Non-printing characters in the string are ignored; if the resulting string is
empty, it is ignored. If it starts with an alphanumeric character, a leading
colon is inserted.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
If maildir_use_size_file
is true, Exim implements the maildir++ rules for
storing quota and message size information in a file called ‘maildirsize’
within the toplevel maildir directory. If this file does not exist, Exim
creates it, setting the quota from the quota
option of the transport. If
the maildir directory itself does not exist, it is created before any attempt
to write a ‘maildirsize’ file.
The ‘maildirsize’ file is used to hold information about the sizes of messages in the maildir, thus speeding up quota calculations. The quota value in the file is just a cache; if the quota is changed in the transport, the new value overrides the cached value when the next message is delivered. The cache is maintained for the benefit of other programs that access the maildir and need to know the quota.
If the quota
option in the transport is unset or zero, the ‘maildirsize’
file is maintained (with a zero quota setting), but no quota is imposed.
A regular expression is available for controlling which directories in the
maildir participate in quota calculations when a ‘maildirsizefile’ is in use.
See the description of the maildir_quota_directory_regex
option above for
details.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
If the mailstore_format
option is true, each message is written as two
files in the given directory. A unique base name is constructed from the
message id and the current delivery process, and the files that are written use
this base name plus the suffixes ‘.env’ and ‘.msg’. The ‘.env’ file
contains the message’s envelope, and the ‘.msg’ file contains the message
itself. The base name is placed in the variable $mailstore_basename
.
During delivery, the envelope is first written to a file with the suffix ‘.tmp’. The ‘.msg’ file is then written, and when it is complete, the ‘.tmp’ file is renamed as the ‘.env’ file. Programs that access messages in mailstore format should wait for the presence of both a ‘.msg’ and a ‘.env’ file before accessing either of them. An alternative approach is to wait for the absence of a ‘.tmp’ file.
The envelope file starts with any text defined by the mailstore_prefix
option, expanded and terminated by a newline if there isn’t one. Then follows
the sender address on one line, then all the recipient addresses, one per line.
There can be more than one recipient only if the batch_max
option is set
greater than one. Finally, mailstore_suffix
is expanded and the result
appended to the file, followed by a newline if it does not end with one.
If expansion of mailstore_prefix
or mailstore_suffix
ends with a forced
failure, it is ignored. Other expansion errors are treated as serious
configuration errors, and delivery is deferred. The variable
$mailstore_basename
is available for use during these expansions.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
If neither maildir_format
nor mailstore_format
is set, a single new
file is created directly in the named directory. For example, when delivering
messages into files in batched SMTP format for later delivery to some host (see
section Outgoing batched SMTP), a setting such as
directory = /var/bsmtp/$host |
might be used. A message is written to a file with a temporary name, which is
then renamed when the delivery is complete. The final name is obtained by
expanding the contents of the directory_file
option.
[ << ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This document was generated on April 14, 2011 using texi2html 1.82.