What I am seeing is lots of SMTP connections from various authorized clients
that are stuck in the data portion of sending a message. After so many of
these connections the SMTP server complains the MaxClients has been
exceeded. I have increased this from 12 to 25 and same results. I have one
user who has called so far complaining he is unable to send email. In
looking at a netstat -a I see that he has around 12-15 connection in the
ESTABLISHED state at any given moment and all of the sendmail logs show
nothing past DATA for those connections. The mailq shows lots of "no control
file" for all of his connections as well as several others.
Soon after SMTP dies on receiving email. A stop and start of sendmail fixes
for about 30 minutes. Load averages look ok, nothing to bad.