Is it possible to configure Postfix on Plesk to use Smart host on per domain basis?

Question

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

Answer

Such functionality is not implemented yet, you can vote it 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 customizations were not tested properly and do not officially supported by Plesk, so perform it at your own risk. Refer to the Postfix official documentation for more information.

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