Sendmail Tuning For Batch Mail Jobs

Kyle,

** I'm by no means a sendmail expert **

In your use case, the need for sendmail to accept / queue up the messages asap is key(batch processing?). If you haven't, take a look at sendmail options: QueueLA and RefuseLA - Queue Load Average and Refuse Load Average. If you are really bombarding sendmail your load averages will go through the roof quickly and you'll hit RefuseLA which might be part of your timeout issue. You may want to increase RefuseLA (if you haven't already).

To keep sendmail from doing too much at once (receiving and transmitting) lower your QueueLA. A lower value of QueueLA will put sendmail into queue only mode so sendmail will focus on queuing work and save the transmit / sending work for later. A low QueueLA and high RefuseLA will result in the system queueing up large amounts of mail(disk space) then begin sending it out after the load falls below QueueLA.

For normal sendmail configs it is worth noting that QueueLA should not be much lower than RefuseLA, and possibly it should be very slightly higher.

Delivery mode 'q' is an extreme version of a low QueueLA setting, where you'd have to somehow initiate a delivery command to begin outbound message transfer.

Resource: http://www.brandonhutchinson.com/QueueLA_and_RefuseLA.html