Re: [exim] Dealing with "broken" mta

Rafa wrote:

> control. My problem is, that server is configured to return "450" for
> invalid mailboxes, causing exim to interpret it as a temporary error.

This is broken, wrong and stupid.
4xx tells other MTAs to retry, but as they'll never accept that mail,
there is no point in doing so.

> 1. Tell the other admins to fix their server. I've already did that

The only sane way.

> 2. Have them send me they user list and have exim check against it

That's also a good thing. You won't have to accept mail that will be
bounced. Synchronising should be automatic, but that's easy to do with
scp, rsync, ftp...

> 3. Write my own recipient verification program and call it from an ACL
> using "run" or "readsocket". I think I'm going to do this anyway as

Which will not work if their server is down, and that's just the time a
backup mx is needed. Except for some spammers using the lower priority MXs
by default assuming that they have looser spam checking.

> 4. Setup a special transport for them (and maybe other "broken" mta I
> manage to run across. The problem (and the point of this mail): how

There's no way to do that (AFAIK). And you shouldn't do it.

> 5. Stop providing secondary MX for them. This might be what's needed

That depends on your relationship. I'd be reluctant in supporting such
broken setups.