OT: All processes of Sendmail stuck... DDOS?

[Ugo Bellavance]

Hi,

	I used to have 30 sendmail processes max, but raised it to 100 
yesterday because almost all of the 30 processes were "busy" waiting for 
input from other servers.  I also reduced the timeout value for the "TO" 
command.  2 kind of entries show up in "ps aux | grep sendmail":

sendmail: server h090.n068.nhk.or.jp [133.127.68.90] cmd read

or

sendmail: server nat.resnet.mc.edu [64.246.212.52] startup

Most of our MX's are having this problem.
Using a mix of Greet pause, connexion throttling, greylisting, RBLs.

The number of connexions rejected by sendmail by these different 
processes have known a very significant increase lately.  Before 
implementing Greylisting, MailScanner was processing ~ 100 000 msg/day 
max on all of our servers.  Now all the log entries for rejected 
connexions by sendmail totals ~ 400 000/ day, and it doesn't look like 
it si going to stop.

We are not getting complaints (yet), and the ressources seems to be able 
to cope with the problem without significant problems.

Anyone experiencing the same thing?  Any solution?

Regards,

Ugo