Willif,
The situation is not always as it appears. In my sendmail.cf file there was a line:
O MaxRecipientsPermessage=10
I was told the statement is usually remarked out with a #. Somehow(?) the statement lost it's # and my users could send messages to no more than 10 recipients at a time. Surely you can see where 10 is too low. I have an account that has 55 users and couldn't send interoffice memos.
In an effort to be cyber-responsible, I only increased the threshhold to 100 as opposed to unlimited. It's working as I expected.
Thank you and to stfaprc for replying.
TGraz