Hi Roshan,
Based on my experience, the issue may occur in Cathed Exchange Mode. As far as I know, when two different users update the same item, independent of each other. The user will get an error with the conflict information in the status bar. At that time, there could be a potential data loss as a result of one of the items taking precedence over the other one. You can see the message appears in Conflicts Folder in Sync Issues.
To troubleshoot the issue, I would like to confirm if it is working at OWA(mail.office365.com). In addition, what’s the detailed version of Outlook client? Is it Outlook 2007 or else? In this case, we can try the following steps to check if there is any improvement.
1. In Outlook client, turn off Cached Exchange Mode and disable the offline Use.
2. Restart the Outlook client and have Outlook email items sync for a while.
3. Enable the offline Use and rename .ost file
4. Enable cached mode
Thanks,
Johnny Zhang