Is it possible to configure Postfix on Plesk to use the Smarthost on per domain basis?

Question

Is it possible to configure Postfix on Plesk to use the Smarthost on per domain basis?

Answer

Such functionality is not implemented, you can vote for this functionality on Plesk UserVoice:

https://plesk.uservoice.com/forums/184549-feature-suggestions/suggestions/5733652-smarthost-external-smtp

The top-ranked suggestions are likely to be included in the next versions of Plesk.

Note: it is possible to configure Postfix to use Smarthost per domain basis via Postfix configuration. Such customisations were not tested properly and do not officially supported by Plesk, so perform it at your own risk. Refer to Postfix official documentation for more information.

Note: Any customization made in Postfix configuration can be overwritten by Plesk Update (for example, in case of bug fix, when configuration files are updates), Plesk Upgrade or by mchk utility, which resets default mail server configuration.