Sendmail Thrashing CPU Endlessly

["Daniel W" <daniel.watts@lincoln-oxford.com>]

Extract from "top":

===============================
12:10pm  up 4 days, 27 min,  1 user,  load average: 1.24, 1.37, 1.23
82 processes: 76 sleeping, 5 running, 1 zombie, 0 stopped
CPU states:  4.4% user,  0.5% system,  0.0% nice,  8.3% idle
Mem:   262144K av,  258592K used,    3552K free,   17440K shrd,       0K
buff
Swap:  262144K av,    3704K used,  258440K free                  146500K
cache

PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME COMMAND
20144 root      13   0  2656    2656  1904      R         94.5       1.0
28:34     sendmail
23448 root       3   0   1096    1096   832       R         5.6         0.4
0:00       top
===============================

You can see from the above that the sendmail process is hogging virtually
the entire CPU. This goes on permanently (this extract is actually soon
after i killed the sendmail process - if I didn't it would go on forever).

I am running a mail server with perhaps 1000 users but I still don't see why
this would cause sendmail to have to operate THIS hard.

The problem is that whilst sendmail is doing this the load average slowely
climbs. I've had load averages of 40+ and long before that services start to
die. All horribly messy.

If anyone could give me a few clues as to what could be causing this I'd be
most grateful!

Sendmail version is:  Sendmail 8.11.6/8.11.6
Red Hat Linux release 7.1 (Seawolf)

Thanks,
Daniel