[Mailman-Users] Using Mailman with Multi Mail Server

Mark Sapiro mark at msapiro.net
Thu Oct 29 17:54:45 CET 2009

Stefan Förster wrote:

> 3. If mail is leaving your MTA at a slow rate but the delivery from
> Mailman to the MTA is fast, try running several queue runners and
> specify an SMTPHOST wit a DNS record pointing to several addresses
> (I'm not really sure about this one, perhaps Mark could clarify).

If I understand the OP's situation, this probably won't help. I think it
is a case of a single post to a large list. In this case, a single
OutgoingRunner will handle the message and the other runners will do

The idea of multiple addresses in DNS for SMTPHOST is that multiple
connections to SMTPHOST *may* connect to different servers, but in the
short term, this probably doesn't work, because this depends on the
authoritative DNS returning the A records in different order, but once
we look up SMTPHOST, we may not ask again before TTL expires. Multiple
addresses for a name in DNS works for load balancing of a lot of
incoming connects from multiple sources. I'm not sure it works well or
at all for outgoing connects from a single source.

However, if the multiple A records does work in the short term, it may
help even in the large list scenario because SMTPDirect will close and
reopen the connection to SMTPHOST every SMTP_MAX_SESSIONS_PER_CONNECTION
chunks, so if you set SMTP_MAX_SESSIONS_PER_CONNECTION to a small
positive number, you may connect to a different IP for successive
connects to deliver the one message.

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

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