Starting in early 2022 Google started sending out messages similar to this:
To help keep your account secure, from May 30, 2022, Google no longer supports the use of third-party apps or devices which ask you to sign in to your Google Account using only your username and password.
The solution is to use an “app password”.
- Go to https://myaccount.google.com/ and ensure that you are logged in as the same account you are configuring for Postie.
- Under “Security”, activate the the “2-steps verification” on the Google account.
- Once it’s activated, set “App passwords”, “Select App” to “Mail”, “Select device” to “Other (custom name)”, give it a name (Postie Password) and copy the password generated at the end of the “App passwords” process.
- Use the generated password on Postie instead of the Google account password.
https://support.google.com/accounts/answer/185833
Note that you will need to enable 2-Step-Verification for your domain if the App Password option isn’t available.
If this solution doesn’t work for you the solution is either
a) Don’t use GMail for your secret Postie email. Use a different provider that supports IMAP or POP.
b) Use a GMail email, but forward all emails to a different provider that supports IMAP or POP.