All of a sudden access to my email hosted on Cloudron stopped working - I was getting Auth Failed from Rainloop, RoundCube and my android clients. Checked email settings via Cloudron UI - tests were fine, users and accounts as expected. But email server was not accessible.
What's worse - emails were not being delivered during the time I was unable to connect, which is a serious issue. I've just got emails that were sent hours ago.
Re-configuring Rainloop (similar to fixing OpenVPN issue of hanging) all of a sudden fixed the issue - now my android client, Rainloop and Roundcube all allow me to log in just fine.
3 main questions:
- WTF?

- Where do I look for details to figure out what's going on? And what should I be looking for?
- Any better way fixing email rather than re-configuring a mail client?