Why are my emails displaying as “on behalf of” or “via” in some mail clients?
Regardless of your From address settings which you choose for each message, it may happen that some of your subscribers see:
From: firstname.lastname@example.org on behalf of [[your_from_email]]
The situation described above may occur for only some of your subscribers using certain email clients and email applications like gmail and outlook. Unfortunately, this setting is determined by the email client and is not something that GetResponse can control.