Remember that alertmanager is the sender of the E-mail, not the receiver, so it doesn't need to know the receiving user's credentials. This means you can:
- Configure your own local SMTP server, and use it to deliver messages to
x...@gmail.comor
- Create another username in your GSuite/Google Docs account, just for alertmanager to send E-mail notifications, which doesn't require 2FA
or
- Create a free
gmail.com account, and use it for delivering E-mail notifications (beware you might hit some rate limits if you send too many alerts)