Ordinarily (beginning with V8.6 sendmail), there
is no limit to the number of queued messages that can be processed
during a single queue run. If there are more messages than
sendmail has allocated memory for,
sendmail will calmly allocate more memory.
(Previously, a fixed limit was imposed at compile time.)
Some systems process so much mail that a single queue run can become
unmanageably largeso huge, in fact, that system resources are
strained to the limit with an adverse effect on system performance.
If your site suffers from this problem, beginning with V8.7 you can
set an upper limit on the number of queued messages to be processed
by using the MaxQueueRunSize option:
O MaxQueueRunSize=limit configuration file (V8.7 and later)
-OMaxQueueRunSize=limit command line (V8.7 and later)
define(`confMAX_QUEUE_RUN_SIZE',limit) mc configuration (V8.7 and later)
Here, limit is of type
numeric and defines the upper limit on how many
queued messages can be processed during a single queue run. If
limit is less than or equal to zero, if it
is missing, or if the entire option is missing, no limit is imposed.
The default is to impose no limit.
If MaxQueueRunSize is defined and if that limit is
reached while processing the queue, sendmail
will log the following message at LOG_ALERT:
WorkList for queuedir maxed out at limit
Processing of the queue is described in Section 11.7.
The MaxQueueRunSize option is safe. Even if it is
specified from the command line, sendmail
retains its special privileges.