Thanks. Looks like they fixed this quite a while ago and now either you can verify an account after which it will accept your From header (and the web and app U

Thanks. Looks like they fixed this quite a while ago and now either you can verify an account after which it will accept your From header (and the web and app UIs let you select that) or, if you haven’t verified the address then if you send an email through their SMTP servers it will rewrite the From as your gmail address and sets a new X-Google-Original-From header to the address you put in the email originally.