Gmail and Microsoft require an app password (not your normal login password) if 2FA is on.

After saving, you'll get a unique webhook URL. Install an SMS-forwarding app on the Android phone (e.g. SMS Forwarder or SMS Gateway from the Play Store) and point it at that URL with a JSON body containing the sender and message, e.g. {"from":"{{sender}}","message":"{{message}}"} — exact template syntax depends on the app.