Syncronization Logs in Outlook 2007 / 2010 With Online Exchange

This article from Tony Redmond says it all

Most synchronization issues are caused by Network issues or the user looking at their email on two different devices such as a PC and tablet or phone. This is not isolated to one hosting provider either.

TONY REDMOND  Link to full article

Outlook 2007 and Outlook 2010 generate synchronization logs when errors occur when clients synchronize local replica copies (held in the OST file) of cached server folders. Logically, synchronization errors and log generation only happens when Outlook is configured in cached Exchange mode.

There are many reasons why a synchronization operation might experience some difficulties. Network glitches are the obvious example – something that is extremely likely to happen when connecting Outlook to Exchange Online in Office 365 when transient network errors are common between the network that the PC client runs on and Microsoft’s datacenters. After all, no one controls the Internet and no one guarantees the speed, latency, or reliability of an Internet connection. Figure 1 shows a synchronization log that reports some network problems between Outlook 2010 and my Exchange Online mailbox.