Re: [msmtp-users] Feature request: MX lookups

[Mary Gardiner <mary@...159...>]

On Sat, Aug 30, 2008, Martin Lambers wrote:
> MX lookups, just like queueing or local deliveries, are beyond what
> msmtp was originally intended to do. In my opinion, a real MTA should be
> used for this. What's wrong with postfix?

Thanks for your notes. I'm thinking of a slightly different (and
simpler) use of MX records than your notes seem intended for, and
probably more suited to the msmtp use-case, I hope. Your notes seem
intended to deliver each outgoing mail directly to its email domain's
MX. Eg, joe@...45... goes to example.com's mail exchangers and
jane@...165... to example.org's mail exchangers. I agree that this is
more suited to something like Postfix!

The feature I was thinking of was instead that the user still specifies
only one outgoing mail relay: relay.example.com. However, instead of
(only) doing an A record lookup on example.com, getting IP address
0.0.0.0 and attempting delivery through 0.0.0.0 only, that msmtp could
instead do an MX record lookup on relay.example.com, receive several
answers, eg mx1.example.com, mx2.example.com and attempt delivery
through each of them in order of priority of their MX record. This is
somewhat more complex than the current behaviour as failures must be
tracked a little, but not as complex as trying to determine the correct
MX on a per email basis: there's still no parsing of addresses.

The relay could be specified in either of two ways:
 - a new config variable, eg "mxhost relay.example.com"
 - preference for MX lookups and fallback to the existing behaviour
   (this happens to be what Postfix does)

This should be considerably easier to implement than direct connections
to each email's intended MX.

-Mary