[Mailman-Users] Google mail servers reply "Multiple destination domains per transaction is unsupported "

[Stephen J. Turnbull]

Mark Sapiro writes:

 > It's hard to say, but it seems that you have list members in multiple
 > domains all served by the same google mail MX, and google doesn't like
 > receiving multiple recipient domains in a single SMTP transaction.

Other way around, I think.  The Google MX in question seems to be
Max's smarthost.  I don't think any MTAs are so "smart"[1] as to try
to collect MXs for all the domains they're sending to, and then send
to multiple domains via any MX that serves multiple domains.

 > I don't know about whitelisting, but if you set
 > 
 > SMTP_MAX_RCPTS = 1

This will still do the trick.

Footnotes: 
[1]  Yes, I know about qmail.  Not even djb ...!