Hovus,
Sorry I haven't replied sooner to your question.
To keep things short as my original try at this question took too long and I got kicked out.
POP3 and IMAP is for receiving messages and the supported format for the 5000 is IMAP. The basic difference between the two is synchronization of clients as POP3 doesn't and IMAP does. SMTP is for sending messages which for you is obviously working.
Now, the issue. There are two methods to email synchronization Event and Polling.
Event uses the IDLE command to recieve messages as they happen, but every once in a while this fails with a NULL reply between the email server and the voicemail system. When this happens the synchronization thread fails and one of the issues this causes is duplicate emails. Changing to the Polling Method forces the Voicemail to go out periodically to get a status change. The good thing is the Polling Method is less overhead for the Voicemail, but it is not as responsive as the Event Method; and we all know how the customers wants to see things happen in relative real time. So basically the Mitel TS person was going through the first step in trying to figure out if the problem is with the type of synchronization you are using between the email server and the voicemail.
Hopefully that is clearer than mud and if you want a more detailed explaination on how this works then just let me know and I will type something up and paste it in next time. lol
Thanks,
TE