Mark, thanks for the very detailed info below. I am still stuck on this.
This sendmail server is setup to relay the mail to smarthost. When I inject a test mail on port 25 with RCPT and FROM to be a made up junk domain, the email is still delivered *immediately* to the smarthost, there is no resolver issues.
If sendmail was really doing DNS lookups, I would think it would be stuck locally or throw a bounce/error right away. It just seems like it's running serially, and not dequeueing multiple messages to the smarthost at a time.
Anil PS: Putting a local DNS cacheing server is a possibility, but not yet.
On Feb 1, 2012, at 10:56 PM, Mark Sapiro wrote:
Anil Jangity wrote:
Does mailman actually (if it works) send to 15 recipients at a time - per SMTP session?
Mailman's use of the term session is not consistent with the RFCs. What Mailman calls SMTP_MAX_SESSIONS_PER_CONNECTION is actually in RFC 821, 2821, 5321 terms, max transactions per session. I.e. one session is one connection from HELO/EHLO to QUIT and one transaction is one MAIL FROM and everything that follows up to the next MAIL FROM.
Unless you have some specific MTA reason for setting SMTP_MAX_SESSIONS_PER_CONNECTION, you should leave it at the default value of 0 meaning unlimited.
If a message is personalized or VERPd, SMTP_MAX_RCPTS is ignored because you can't send a personalized or VERPd message to more than one recipient. Otherwize, SMTP_MAX_RCPTS is the maximum number of RCPT TO recipients in one MAIL FROM transaction.
Note that 6000 users per 35 minutes is less than 3 per second. This is extremely slow. I typically see 30 to over 60 recipients per second on a rather ordinary production server with full VERP.
See my reply to your original post in this thread at http://mail.python.org/pipermail/mailman-users/2012-January/072778.html and look at the FAQs linked in that post for hints. In particular, do not do DNS verification of RCPT TO domains during SMTP from Mailman.
-- Mark Sapiro mark@msapiro.net The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan