This issue to sync messages using a google account has started
stopped syncing messages !!
Google hat announced to turn off "less secure apps" by 30th of May 2022 – they did it on 7th of June (yesterday). Btw.: there should be a (theoretical) possibility to circumvent that with "Google App Passwords"; but to use that you need to activate 2FA – but 2FA needs a phone number to work; a second eMail account (outside of gMail) is not usable for that).
- Windows 8.1