Infamous "Connection to IMAP Server failed" won't go away.

[sm69th]

I have googled this error to death and can't figure out how to fix it. Hopefully someone can help!

I have roundcube installed on the same server as HMS (hMailServer). Everything works great and then all of a sudden "poof", roundcube won't let anyone login, it just throws:

"Connection to IMAP Server failed"

followed by:

IMAP Error in C:\Websites\webmail.mydomain.com\program\include\rcube_imap.php (142): Empty startup greeting (555.555.55.555:143)

Any ideas? If I reboot the server it all starts working again, but this sporadic IMAP issue is driving us nuts.

[SKaero]

Its a problem with your IMAP server, try looking at your IMAP servers logs.

[sayce]

Solution is below.
Add your internet ip to white listing under Anti-spam of hMailserver Administrator window.