Add support for Oauth 2.0 for mail authentication

Microsoft and Google have decided to disable basic authentication for mail protocols. 

We should basically switch to Oauth 2.0 for mail authentication.

More info:

https://www.bleepingcomputer.com/news/security/microsoft-and-google-postpone-insecure-authentication-removal/

There are also some issues for Atlassian (add support for Oauth 2.0 in Jira) but seem to not have gathered enough interest  

https://jira.atlassian.com/browse/JSWSERVER-20381

https://jira.atlassian.com/browse/JRASERVER-63917