Recently, I found that POP3 and IMAP were failing to start on my backup VPS server, with cPanel/WHM. It’s not a major problem as its main task is to handle backup DNS and mail, but I do still use POP3 to collect the occasional mail from it.
If you have notifications switched on, and monitoring, you will also keep getting e-mails saying cpanel was unable to automatically restart it.
Even manually trying to start POP3 and/or IMAP fails, giving something similar to the following error messages:
Waiting for cppop to restart..............finished.
couriertcpd is disabled
Service: [cppop] has been disabled by the sys admin
And also when you try and start IMAP:
Waiting for imap to restart..............finished.
couriertcpd is disabled
Service: [imap] has been disabled by the sys admin
After some research, it seems that the IMAP server has to be running in the service manager. To start it, log in to WHM, scroll down to "Service Configuration" in the navigation menu on the left, and click "Service Manager". In there, enable the IMAP server and the monitor if you want its status checked automatically.
You should now be able to start POP3 and IMAP.