Mail handlers: Differentiate between inbound and outbound email

Hi all,

this question is about the Mail Handlers feature in Plesk 12.5 for Linux (https://docs.plesk.com/en-US/12.5/extensions-guide/mail-handlers.71844/). I'm using Postfix.

I've added a before-queue mail handler to Plesk in order to filter some messages before they are queued. This handler is being called for inbound messages (= from other hosts) and outbound messages (= from my host to other hosts). Is there any way to differentiate between these two types? I'd like to only...

Mail handlers: Differentiate between inbound and outbound email