Ok, if it happens again, we'll look at what's there in the DB. It seems to have been "stuck", somehow, since the authentication info we were using was the same before the error, during the error, and after the error was fixed by deleting and recreating all accounts.

Anyway, thanks, both, for your help looking at these issues!

I know this is a somewhat old thread, but our exact same initial problem has recurred:

We suddenly started getting error alerts stating "Mail Fetch Failure Alert" and "Too many login failures." Despite receiving this alert, the system continued receiving e-mail tickets for a few more hours, but then stopped. We confirmed the account is not locked. It is an Microsoft 365 account, and we can successfully log into the mailbox using the same password as is configured in osTicket. Also, the Microsoft 365 logs shows all of osTicket's login attempts, and it shows that they are successful! We are also able to send outgoing e-mail successfully using this account from the osTicket Diagnostic tool.

Last time, the solution was to completely delete the e-mail account and re-add it. Though that process ran into several snags due to confusion in how osTicket thought the e-mails were configured, it did work once we were actually able to re-add it. This time, however, we avoided that snag but still cannot re-add the e-mail due to the "too many login failures" error.

Why does this seem to reoccur every few months, and why does osTicket think there is a login failure when we know the settings and credentials are correct, and haven't changed at all throughout any of these failures? What can we check into?

Thanks!

Just an update for anyone who comes across this thread: this time, the issue was that OAuth is now required for osTicket to connect to M365.