QueueLA and RefuseLA

By default, sendmail will reject MTA/MSA connections when the system load is 12 * number of processors, and operate in queue-only delivery mode when the system load is 8 * number of processors.

$ egrep "QueueLA|RefuseLA" /etc/mail/sendmail.cf
#O QueueLA=8
#O RefuseLA=12

From cf/README:

confQUEUE_LA            QueueLA         [varies] Load average at which
                                        queue-only function kicks in.
                                        Default values is (8 * numproc)
                                        where numproc is the number of
                                        processors online (if that can be
                                        determined).
confREFUSE_LA           RefuseLA        [varies] Load average at which
                                        incoming SMTP connections are
                                        refused.  Default values is (12 *
                                        numproc) where numproc is the
                                        number of processors online (if
                                        that can be determined).

For dedicated mail servers, the value of RefuseLA should be greater than the value of QueueLA. Mail should not be accepted faster than it can be processed, as mentioned in sendmail/TUNING:

It is important not to accept mail
faster than it can be delivered otherwise the system will be
overwhelmed.  Hence RefuseLA should be lower than QueueLA, the number
of daemon children should probably be lower than the number of queue
runnners (MaxChildren vs. MaxQueueChildren).

Also, read this comp.mail.sendmail post.

Note: when defining QueueLA and RefuseLA, sendmail does not multiply the values by the number of processors; values are absolute.

 Example sendmail.mc directives for a QueueLA of 51 and RefuseLA of 50, respectively:

define(`confQUEUE_LA', `51')dnl
define(`confREFUSE_LA', `50')dnl

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Last modified: 2006/03/30