Google G Suite: Sending via smtp.gmail.com will alter the From Address
If you're using Google G Suite, send email via smtp-relay.gmail.com rather than smtp.gmail.com.
If you use smtp.gmail.com then the FROM header in the email will be a mashup of the From Address and the SMTP Username.
For example ...
- Say my SMTP Username is set in Settings - Outbound Mail to email@example.com
- Say I use the following From Address in my CiviMail: My Name firstname.lastname@example.org
- The FROM header in the email will be From: My Name email@example.com
Using smtp-relay.gmail.com does what you expect.