On Tue, Apr 21, 2015 at 09:50:05PM +0200, josef radinger wrote:
> a domain xy.org which has users on two servers: one exchange server (B)
> and one postfix(A). in front of that two systems is another portal-host,
> which cannot distinguish between mails for users on system A or on
> system B and therefor send everything to A.
What software does this portal host run? Does the portal host do
any recipient validation, and if not why not?
> users will get moved from exchange to postfix in batches
Presumably (or ideally) Exchange has forwarding addresses configured
for the users who are moving, and therefore should have a complete
list of all valid users in LDAP.
> and I would like to do the following:
>
> Postfix is the leading system and will receive all mails.
Fine.
> If a user is not already on postfix (and would generate a
> "User unknown in virtual alias table") then the mail should be sent to
> the exchange host.
There is no need for "unknown" users, all users should be "known", and
appropriate rewriting and/or transport rules will direct their mail to
the right place.
> I know this is not ideal, because of the possibility of backscatter.
It is sloppy, and unnecessary. If the domain is a virtual alias domain,
each user needs to be aliased to a real domain (u...@mailstore.example.com
where u...@example.com is the original virtual address, and "mailstore"
varies by user to route either to Exchange or local delivery).
--
Viktor.
