When sending an email, via SMTP, from a Gmail account with a different From address to the account name the email arrives ok, but the From address has been ignored. We are still seeing the account address not the From address.
Gmail doesn't allow using a different From address than the the account's username.
From address is changed by the SMTP server.
If you are trying to implement VERP for easy bounce processing read this: https://www.limilabs.com/blog/verp-variable-envelope-return-path-net
I was afraid that was going to be the answer. Thank you