We had a fully working Jira Service Desk installation (JIRA Service Desk Application v3.6.1)
for years and on Friday we changed the password of the associated email account ithelp@...
Once the change was done on the Exchange server we updated the password on system-Outgoing Mail and system-Incoming Mail. The test in both cases says its working.

If we check Mail audit log for ithelp@... then we see.
If we do a test there then:

And the "view log" shows:

What have we tried?
We went through https://confluence.atlassian.com/jirakb/troubleshooting-jira-service-desk-incoming-mail-790960076.html?_ga=2.74568658.1933816762.1551665594-977289960.1550604024 without success.
Restarting Tomcat.
Rebooting the server.
Deleting and recreating the configuration for IMAP.
Configuring the IMAP settings using IP instead of name.
If you know what could be the problem or if you know what we are missing your help is greatly appreciated.
Thanks in advance,