Maickel Pandie wrote:

I have some question. in average, How many domain in one list of mailing list in your server? because refer to RFC 2821 message always be sent once for one domain

I'm not sure what you think RFC 2821 says, but in the case of Mailman, messages are delivered to the MTA in SMTP transactions with as few as 1 and as many as SMTP_MAX_RCPTS (default 500) recipients per transaction depending on things like VERP and personalization. Each of these transactions will be considered a separate message by the MTA, even if the contents are identical. Further, in the case of large lists, even with large numbers of recipients per transaction, it is not guaranteed that all recipients in a given domain will be in the same transaction.

-- Mark Sapiro <mark@msapiro.net> The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan