Re: [Exim] Opinions sought: hosts_max_try

twells@??? (Tabor J. Wells) wrote on 30.08.02 in <20020830152452.GB4434@???>:

> True. But in my experience most cases where a domain has a lot of MX
> records, they are large and have very good connectivity. The problem is that
> they just handle a lot of mail and have some servers which refuse
> connections. I'm thinking of AOL, Hotmail, Yahoo, etc. So for them it
> generally is a good thing to try as many MXes as possible because you'll
> likely hit one that can take the mail. They rarely timeout connections to
> any of the servers.

Well, some time ago all of AOL's MXes went off the net simultaneously - I
don't remember what exactly broke, but that was the effect.

Many, many MTAs around the world became effectively useless as they spent
huge amounts of time trying each of those many addresses (there were even
more back then) in turn, especially if they had a large amount of mail for
AOL (which is certainly true of all large ISPs).

Since then, people have become more careful with attempting all MXes.

I think someone was working on an RFC describing that exact scenario, but
it seems to not have made it, or at least I can't locate it. It's probably
written up in somewhere, though.

MfG Kai