[SOLVED] Usermin - Failed to connect to localhost:143 : Connection timed out

I'm getting this error when trying to load the usermin mail page. All accounts work fine via desktop IMAP/POP3 clients, but not through usermin. I've searched the forums and think my problem could be related to the use of LDAP - following one thread I installed the missing perl-Authen-PAM package but it didn't appear to make any difference.

I'm super grateful to anyone who can help with this. I can post any logs and provide any config files you might need too, not sure where to start.