[exim] Return-path: and Sender: rewriten?

Using version 4.93
I have several trusted_users = user, they are denied from receiving messages under their unix username
instead they can only send and receive mail under one of several aliases, thunderbird sets their identity.
I'm also log_selector +address_rewrite to get a look at what gets re-written.

The issue I have, the Return-path: and Sender: fields are being rewritten from the user's alias set by thunderbird
back to the unix username, I was wondering how to make it not do that.

This is the log message for this rewrite...
2020-03-20 18:54:10 1jFLv6-00005O-GI "user1234@???" from env-from rewritten as "user@???" by submission mode
The unix username is user here, and user1234 is one of this user's aliases and is set by the thunderbird identity.
The other headers are correct, like From: user1234@ and Reply-to: user1234@...

Randy.