many sendmail processes not stopping

I have a dual sendmail configuration under SuSE-Linux V 10.2
with amavis (amavisd-new-2.4.3), spamassassin (3.1.8 with
perl 5.8.7).

I often have a process list with many sendmail-processes as

"sendmail: lA1HGgwB022093 sender-server [IP]: DATA".

Those processes will stay for a long time (hours ?) in my
process list and do not stop

What can be the reason ? Where I can begin to search and
analyse. What can I do ?

Thanks Harald