> Couple of our list with over 175 subscribers having problem delivering
> messages to all of its members. Some of the messages gets delivered but
> not all. WE have not modified the list configuration and were advised to
> check for "number of recipient per message" and MAXBSMTP was set to 1000.
>
> We never had any problem of this nature before and I am not sure what has
> caused this error message (552 5.5.3 Too many recipients).

It's always best to post the entire error message so a proper answer can
be given.

MAXBSMTP=1000 is pretty typical for a Windows installation. However, this
just means that LISTSERV will bundle a max of 1000 recipients per message
(*.mail file)  to the outbound MTA. It's the MTA that bundles up the
recipients for final delivery. ISPs like AOL, Yahoo and the like will
reject a message which has over something like 25 recipients per message.
Some even as low as 15.

I don't know which MTA your LISTSERV host is using, but I do know that L-
Soft's MTA (LSMTP) can easily configure individual SMTP destinations to
any number of recipients needed for the mail to get through. By default,
LSMTP will send 1 message regardless of the number of recipients. So if
you have 100 AOL'ers, that message would be rejected. If you set AOL to a
Max of 20, then 5 messages would be sent with 20 recipients each, and the
mail would be accepted.