Hi Allen,
Not sure how those tags crept in but I didn't select them initially? Have removed them now.
We had Office 2010 before the service upgrade so have already run the desktop setup and can connect to other accounts on 365 through the same outlook client so I would say that it would be nothing to do with the client myself.
I'm guessing that when the data was migrated from our old Exchange server to 365 that the data was corrupted and is now held corrupt on 365 - would this be possible? If so is there anyway to scan the file(s) for errors?
Thanks for all the help so far.