Try this:
*) Set a per-domain transport for domain "mydomain.com". e.g. smtp:[remote_mx]:25.
*) Set a per-user transport for user "zzz@mydomain.com". Just use the default one: dovecot, then mails sent to zzz@ will be delivered locally.
Thank you!
In the meantime I have created a work-around:
zzzz@mydomain.com is again a iRedMail user. So receive of mail from this is not rejected at iRedmail server (@mydomain).
If another user (for example aaaa@mydomain sends to zzzz@mydomain this goes to local delivery into iRedserver.
There a filter redirects to zzzz@myotherdomain (which then uses the default smtp_auth to MX of provider). from zzzz@myotherdomain it is forwarded again to zzzz@mydomain (ending up at MX).
(A little bit as scratching with the right toe at the left ear but working....)
I will tryout your 2nd suggestion later on.
the per user transport: shall this be entered into field 'transport' in table vmail/mailbox?
Kind greetings from Vienna,
Marcovaldo