I'm having a problem in syncing my hotmail e-mails through IMAP on Mail for mac.

I've followed the steps in How to set up Mac Mail to sync your Outlook.com account to set up my mail in Mail for mac and it seemed to work. The initial sync worked fine, but then after I tried to copy/paste a load of my old POP3 mail from the same hotmail account into the IMAP mailbox, I have started to get issues where Mac Mail never finishes sync'ing. I now have had no new email land in my inbox for 5 days !   :-( 

All the folders under the inbox and all the other mail items such as sent, drafts, junk etc are synchronising but none of the new e-mails in the inbox are showing up.

Can someone please guide me as to what this issue could be and how to fix it ?   I keep occasionally getting the "error 9" messages that other people have received, but mainly I just see the 'activity monitor' sat there saying "Synchronizing with server" for hours on end and then it appears to stop. 

The inbox currently has around 3.5k mails inside, but I have approx 7k I still need to *copy* into this mailbox from my old POP3 mailbox archive.

I have tried shutting down mail and deleting the .OfflineCache folder as per certain blog posts, but to no avail. I have also tried to offline/online the account as well as "enable/disable" the account from inside Mac Mail preferences.

Mac OS X v10.8.5

Mac Mail v6.6

Any help is very much appreciated.