Any Postfix solution for mail server migration?

[Swift Griggs]

How can this be done? I've Googled and there only seem to be vague hints, 
but no solid method to migrate in the way I'm proposing.


---[ Problem Description ]---
Server "Oldserv" = old MTA system I want to get away from
Server "Newserv" = new MTA I want to migrate TO.

1. Mail to flow to Newserv first.
2. If mail is for a local user, the mail stays on the system.
3. If the mail is for an unknown user it's forwarded to Oldserv.
-

I don't want the header getting re-written. So, I see people doing things 
like setting up aliases so that userp...@mydomain.com gets changed to 
userp...@oldserv.mydomain.com. That's unacceptable. It'll hork up the 
user's mail experience and re-write addresses that were fine the way they 
are.


The whole point of this is creating a method where I can migrate one user 
at a time to the new system without having to do a "big bang" migration of 
the whole company at once. The logistics of that are too big for me. So, I 
have to be able to take it on in chunks.


Plus, I'm not married to Postfix. I'd use Exim or anything else if it'd 
work. The postfix mailing list and IRC channel are super-hostile & 
abusive. I certainly wouldn't be heartbroken to never have to communicate 
with them. This is one of many reasons why I run NetBSD rather than 
OpenBSD ... Community attitude/spirit also matters to me.


This is a simple "checkbox" feature in Communigate Pro, but I'd rather 
stick with open source, given a choice.


 Swift

Re: Any Postfix solution for mail server migration?

[Manuel Bouyer]

On Thu, Jan 21, 2016 at 02:36:25PM -0700, Swift Griggs wrote:
> 
> How can this be done? I've Googled and there only seem to be vague hints,
> but no solid method to migrate in the way I'm proposing.
> 
> ---[ Problem Description ]---
> Server "Oldserv" = old MTA system I want to get away from
> Server "Newserv" = new MTA I want to migrate TO.
> 
> 1. Mail to flow to Newserv first.
> 2. If mail is for a local user, the mail stays on the system.
> 3. If the mail is for an unknown user it's forwarded to Oldserv.
> -
> 
> I don't want the header getting re-written. So, I see people doing things
> like setting up aliases so that userp...@mydomain.com gets changed to
> userp...@oldserv.mydomain.com. That's unacceptable. It'll hork up the user's
> mail experience and re-write addresses that were fine the way they are.

If it's in the alias file this doens't rewrite the headers, only
the envelope. The mail in the final mailbox will still have
the original To: or Cc:

-- 
Manuel Bouyer 
 NetBSD: 26 ans d'experience feront toujours la difference
--

Re: Any Postfix solution for mail server migration?

[Hal Murray]

> 3. If the mail is for an unknown user it's forwarded to Oldserv.

If "forwarded" means store and forward, you don't want to do that.  Consider 
what happens with bogus names, say from a typo.  Your ew system is stuck with 
bounce or drop.  If you aren't familiar with that mess, google for bounce vs 
reject.

I think the solution is to make a list of all the legitimate users on the 
remote system and setup a forwarding table.  It shouldn't be hard, just a bit 
of scripting.


-- 
These are my opinions.  I hate spam.