Use MIAB as smtp server for domains not controlled by it?

1

Hi, I have some domains which I cannot move to my MIAB. For spam control I would however like to be able to use my MIAB to send out the mails for those particular domains.
Is that possible in any way?

2

ok so apparently I had missed the description of this here:
https://mailinabox.email/advanced-configuration.html

What I am still unsure about is whether this will make use of the SPF, DMARC and other anti spam mechanism such that my mails from the remote server will not be marked as spam?

kim