Issue Prevent Postfix from delivering e-mails locally

[JohnBos]

We're currently trying to create a seperate POP/IMAP Plesk server.
Unfortunately we have a few domains that require to host mailboxes on seperate servers (eg. [email protected] towards a ticketsystem and the others to this Plesk server), we use a standalone MX server that separates the mails to send them to the right server.

Now for the the issue:
Plesk makes PostFix deliver e-mails locally if the domain has the mail service enabled, which would cause problems if mailboxes on this Plesk server would try to send e-mails to a mailbox on a separate server (so [email protected] to [email protected] in my example above).

Things we've tried:
The Plesk installer has an option for "MSMTP (relay only)", which would would be enough for us (we have serarate SMTP servers) but selecting this options disables all other mail functionality (removes dovecot/courier etc.)

There's also a support page that addresses this problem, but unfortunately none of the resulutions work for us:

1. Disable the mail service per domain or subscription
   We can't disable the mailservice, we need it for the mailboxes
   
   
2. If the previous steps did not help, check the postfix configuration
   We can't use this one because it only allows to catch extra domains for local delivery, not block any.
3. If the external mail service is used for all subscriptions, it is possible to modify Postfix configuration to exclude domains which exist in Plesk from the local delivery
   This one did work, but the Plesk updater and plesk repair overwrites these changes. We tried several ways to block these rules from getting overwritten but they always get added back.

So the last 2 resolutions would work but they seem too dangerous to use on a production environment with 100+ domains as an update/repair would break it (see also).

 

[homberger]

Did you find a solution to this problem?