Question about Outlook Express

I just got a new mac and downloaded Outlook 2011. I have had the following issues

1) Outlook keeps syncing to the server. The files in the inbox will disappear and then start downloading all over again. This happens sometimes every few minutes. There is no set pattern.
2) Deleted messages dont sync to the server. So if i delete something on Outlook, when outlook resyncs with the server, it is there again.

I have tried -
1) Creating a new identity - did not help
2) Delete the IMAP account and set it up again - still nothing.

I had Entourage 2004 and it worked like a charm. Is this a mac thing or an outlook thing? How do I fix it!?

Nitasha