GSuite Alias

Hi Yehudah,

I’ve been trying to get Post SMTP working to send from a GSuite alias, Admin@. I have ‘admin@’ as the Envelope-From Email Address, and I have successfully granted Post SMTP access to gmail, with the correct OAuth credentials (under the main account brett@), but I keep getting the following error: “Communication Error [334] – make sure the Envelope From email is the same account used to create the Client ID.”

What have I done wrong? I tried following https://postmansmtp.com/how-to-send-email-from-alias-domain-with-gsuite-google-apps/ but no luck.