We have been having a problem lately with our two sendmail machines. We have had them for a long time, and they have always been reliable until recently. Currently these two sendmail machines are our outside relays. They accept mail, then relay to our spam box, which then relays to our Exchange server. This was all working correctly until recently.
Now, several times a day, the two sendmail queues stop. It appears that an email comes into the queue and causes a "451 4.7.1 Please try again later" error. Once that error occurs then all the other emails that appear to come in behind it receive the illegal seek error. The queues then appear to stop.
Generally rebooting will not fix the problem. And it seems that issuing a sendmail -q doesnt always fix it. It seems to me that the machines have to queue up over 100 messages, before sendmail -q will do anything. If I issue before that, it instantly comes back to the prompt. When it does work, the queue clears out, except for the original message that caused the 451 4.7.1.
I am very new to sendmail, and only can relate what I know through trying to diagnose this problem.
Both boxes are running Suse 7.2 with sendmail 8.11.2.
The spambox is a third party appliance running solaris and sendmail 8.12 (I believe)
The email that causes the jam is always a piece of spam, and for some reason is always ~650 bytes.
Any help would be appreciated!!!