Relevant Product: Exclaimer Cloud - Signatures for G Suite
Scenario
Users are sending emails from alias addresses and want to apply different signatures to emails sent from these alias addresses.
Resolution
When an email is sent from an alias email address in Google Workspace, the Return-Path header is populated with the primary SMTP address of the user sending the email.
When emails are processed by Exclaimer Cloud, the user whose signature should be applied to the email is determined by the email address populated in the Return-Path header, so it isn't possible to apply a different signature to emails sent from alias addresses.