Nuntius is a webmail application. It reads messages from IMAP, puts them into an Sqlite database. There is a web-application to view and do email stuff.
Each account is configured in and INI type file in ./etc.
https://github.com/pear/Net_IMAP/blob/master/Net/IMAP.php https://github.com/pear/Net_IMAP/blob/master/docs/test_IMAP.php
https://developers.google.com/gmail/imap/xoauth2-protocol
https://github.com/google/gmail-oauth2-tools/wiki/PhpSampleCode
https://github.com/google/gmail-oauth2-tools/wiki/OAuth2DotPyRunThrough
https://developers.google.com/identity/protocols/oauth2/service-account
https://developers.google.com/identity/protocols/oauth2
https://www.limilabs.com/blog/oauth2-gmail-imap-installed-applications
https://github.com/pear/Auth_SASL
https://packagist.org/packages/google/apiclient
https://github.com/google/gmail-oauth2-tools/blob/master/php/oauth2.php
https://developers.google.com/identity/protocols/oauth2?hl=el
https://developers.google.com/gmail/imap/xoauth2-protocol?hl=el https://support.google.com/cloud/answer/9110914#restricted-scopes
https://tools.ietf.org/search/rfc3501 https://developers.google.com/gmail/imap/xoauth2-protocol