Thanks so much Rolf. The fanout distribution is working fine.  I'll keep the VERP option in the back of my mind to try some other time.  For now, though everything is clicking away like it is supposed to!  Thanks again.

I've just recently started supporting Mercury again, after several years in a different job.  If my memory serves, we used to use mailing lists with large number of users and had no problems with SMTP server limitations on the number of addresses in the message.  It seemed like Mercury was able to break the message up into separate envelopes or something.  I always used SMTP-C 'cause we were on a slow dial-up.

 I've got Mercury 4.61 running and a mailing list setup with a little over 100 members.  I first tried SMTP-C to my website host's SMTP but still get the "too many recipients" message, so decided to try SMTP-E.  There I get a lot of issues about bad connections or refused connections.

 I'd rather use SMTP-C if I can get Mercury to break up the message rather than sending to everyone in one big chunk.

 Any thoughts?

Depending on the number of recipients you might be able to solve it by using "Fanout" distribution:

Explode submissions  For large lists, it can be significantly more efficient to send the message out to several chunks of the subscription list instead of simply generating one large message, since doing so allows multiple SMTP processes to handle the mail at the same time. If you enter a value here, Mercury will "explode" messages sent to the list into that number of outgoing jobs. This setting can have a dramatic impact on list delivery if you are using the MercuryE SMTP end-to-end delivery protocol module. You cannot explode a submission into more than 20 jobs.

If not, you can use VERP based distribution:

VERP stands for "Variable Envelope Return-path Processing": when using this method, every recipient in the list gets a separate copy of every message sent to the list, and in that copy of the message, a special version of the Return-path field is created that allows Mercury to work out the individual list and subscriber from any errors that get returned to it.  

This is selected in the Error handling tab of Mailing list settings.

/Rolf