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Subject: Re: A question on explicit forwarding without DNS query
From: bert hubert (ahuds9a.nl)
Date: Sat Jun 10 2000 - 13:14:41 CDT

On Sat, Jun 10, 2000 at 05:22:30PM +0200, bert hubert wrote:

> Ok - I do remember now. To do this I need to take a step back and rig
> getpwnam that it will return 'no such user' for those accounts that need to
> be forwarded to the big-proprietary-nt-mailserver. At first I tried to solve
> it all within my dict_gecos, but changing getpwnam is also a suitable way.

Ok, this still doesn't work.. luser_relay is a rewrite rule, and doesn't
specify a backup MX server like I thought it would. I've found a solution
but it requires *2* Postfix installations. It works like this:

We receive mail for joe.l.userourdomain.com, and we discover that the
mailbox for this user lives on mx.bigntserver.com. Now, this bigntserver is
completely untouchable, so we need to take the message, still with the same
envelope recipient (RCPT To: joe.l.userourdomain.com), and drop it off at
port 25 of mx.bigntserver.com.

We can't rewrite the addres to joe.l.userbigntserver.com, because the nt
server doesn't recognise that as one of its users. They host many, many
domains on it, and there is no mapping available to us to local usernames.

Now, my solution is like this. If we discover that we need to drop it off at
the NT server, we forward the mail to
ourdomain.com..joe.l.userdirtyhack.ourdomain.com (an additional machine, or
a second postfix on the sameserver), which then recognises this, and
rewrites it as joe.l.userourdomain.com, but we have learned *this* postfix
not to honor the MX records and that the mail exchanger for ourdomain.com is
bigntserver.com ('ourdomain.com
:[mx.bigntserver.com]' in the transport table). It then drops the mail off
at the legacy ntserver, and we're done.

While this would work, it would require two postfixes, and a lot of
administration (>40 domains).

Is something like this perhaps possible:

ourdomain.com local:
ourdomain.com smtp:mx.bigntserver.com

I suspect that this would fail because the local delivery gives a permanent
error, and so any secondary solutions are not used.

I am more then willing to code support for a feature like this, should
people think it has merit for others. I would like hints however on where to
hack the source.

With thanks for your attention & kind regards,

Bert Hubert 

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