Ah right, I forgot about that change sorry I don’t normally use Gmail for sending, it’s usually preferable to control your own mail server since there may be other limitations to contend with on 3rd party/free services like gmail (rate limits, maximum emails/recipients per 24hr period, etc)
It is required that you have 2-Step Verification enabled before you can generate an app-password.
The 16-character password is randomly generated by Google during the process and you can use this password instead of your main account password. The app-password is not recoverable after creating it so make a memo of the password before you close the window, otherwise you’ll have to delete and re-create it