YS Tech,
Yes, the limitations you described are likely due to syncing with IMAP. If you are using the current version of Outlook for Mac - not the New Outlook for Mac - you shouldn't need to worry about your data going through Microsoft's servers, regardless of the protocol you use. With the current version of Outlook, I recommend using EWS if you can to enable the most capabilities within Outlook.
Andrew Barker
Senior Software Developer
SmarterTools Inc.
www.smartertools.com