Norbert Schmidt via Postfix-users:
> Am 07.11.2023 um 17:26 schrieb Wietse Venema via Postfix-users:
> > Viktor Dukhovni via Postfix-users:
> >> On Tue, Nov 07, 2023 at 08:14:04AM -0500, Wietse Venema via Postfix-users
> >> wrote:
> >>
> >>> Another option would be to use the DNS resolver (Bind, unbound, etc)
> >>> support to manipulate zone lookups.
> >> But the OP wants a dedicated transport (for concurrency control and
> >> scheduling), not a change of destination IP, though in a multi-stage MTA
> >> setup that IP could point at a dedicated Postfix instance.
> > I know that, but it was not obvious to me that the OP needs to
> > support high volume.
>
> Actually, I do not need a high volume support. We only want to make sure
> to get our mails delivered to customers who are on M$ infrastructure.
>
> Just changing the IP returned by DNS to a different mail exchange
> provider will not help, as authentication is needed to route mail
> through their infrastructure. To setup a dedicated Postfix instance
> would be an option. It could take care of the authentication when
> contacting the service.
>
> Am I right, at the current moment this cannot be done within Postfix but
> would have to be done in the DNS system, right?
It could be cobbled together with
- An SMTP client in master.cf with the name 'outlook-com' and with
a low process limit.
- A transport_map based on Postfix built-in tcp_table(5) or
socketmap(5), that takes a query with a recipient address or domain,
that looks up MX records, and that returns "outlook-com:" when a
domain has an MX name that ends in .mail.protection.outlook.com
etc. But these lookups happen in time-critical code that blocks
while waiting for a response, so it would drag down mail delivery
performance.
Wietse
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