Mail Delivery Modes
As noted previously, Exim is able to deliver messages immediately or
queue them for later processing. All incoming mail is stored in the
input
directory below
/var/spool/exim
. When queueing is not in
operation, a delivery process is started for each message as soon as
it arrives. Otherwise, it is left on the queue until a
queue-runner process picks it up. Queueing can be
made unconditional by setting queue_only
in the
configuration file, or it can be conditional on the 1-minute system
load by a setting such as:
queue_only_load = 4
which causes messages to be queued if the system load exceeds 4.[117]
If your host is not permanently connected to the Internet, you may want to turn on queueing for remote addresses, while allowing Exim to perform local deliveries immediately. You can do this by setting:
queue_remote_domains = *
in the configuration file.
If you turn on any form of queuing, you have to make sure the queues
are checked regularly, probably every 10 or 15 minutes. Even without
any explicit queueing options, the queues need to be checked for
messages that have been deferred because of temporary delivery
failures. If you run Exim in daemon mode, you must add the
-q15m
option on the command line to process the
queue every 15 minutes. You can also invoke exim
-q from cron at these intervals.
You can display the current mail queue by invoking Exim with the
-bp
option. Equivalently, you can make
mailq a link to Exim, and invoke
mailq:
$ mailq
2h 52K ...
Get Linux Network Administrator's Guide, Second Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.