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Re: Question regarding virtual alias rewriting

From: Colin Campbell (sgcccdccitec.qld.gov.au)
Date: Tue Mar 04 2008 - 21:23:26 CST

Hi,

On Tue, 2008-03-04 at 22:09 -0500, Victor Duchovni wrote:
> On Wed, Mar 05, 2008 at 11:25:49AM +1000, Colin Campbell wrote:
>
> > Hi,
> >
> > I have a setup as follows:
> >
> > Host A: running Exchange, handles email for example.com. Some users are
> > local and some are "remote". Users that aren't local are sent to Host B.
> >
> > Host B: running Postfix, rewrites (virtual_alias_maps) example.com to
> > example.net and uses Host C as relay host.
>
> Unconditionally, or only for the known mail accounts that are "remote"?

There's a loaded question if ever I saw one :-). Right now the answer is
unconditional. The best I can hope for is that the sending end, Host A,
will weed out the unknown "remote" accounts. I will chase that up.

> > Suppose user1example.com sends an email to user2example.com, "user2"
> > being one of the "remote" users. The email is forwarded from Host A to
> > Host B. Host B then rewrites user2example.com to user2example.net and
> > tries to send to Host C. Unfortunately host C is down, the email is
> > delayed and Postfix sends a delay notification.
> >
> > Will the delay notification be subject to the virtual_alias_maps
> > rewrite? (ie will user1example.com be rewritten to user1example.net).
> > If so, what's the best method of stopping this? All suggestions welcome.
>
> Yes, all recipients are subject to rewriting.

Which is bad, for me. I guess then the solution is a second instance on
Host B. I'll do the rewrite in the first instance and pass the email to
the second one. Since the second instance will "always" be there, any
problems with Host C will be handled in the second instance which won't
rewrite. Correct?

>
> > I guess I should also ask if virtual_alias_map is the best way to handle
> > this. Is it?
>
> It is, but don't create rewrite rules that incorrectly rewrite too much.

Colin
--
Colin Campbell
Unix Support/Postmaster/Hostmaster
Citec
+61 7 3227 6334