In all versions of Microsoft Outlook since 2003, exchange email accounts have a Cached Exchange Mode option that allows outlook to “cache” or store mailbox data on the computer it is installed on.
When using Exchange Online services, the communication channel is based on a WAN infrastructure, which by default, have narrow bandwidth verse LAN infrastructure.
In this scenario, we will need to find additional “factors” that can cause the synchronization problems such as local plugins or add-on that installed on the user desktop, anti-virus application, local hardware, etc.
In this section, we review to optional causes for Outlook synchronization problems. Desktop Hardware As mentioned before, when using the Exchange Online services, the synchronization process is created using WAN infrastructure (communication over the public network).
(The synchronization process “direction” is from the local desktop to the cloud).
In case that the synchronization process fails, we will need to eliminate the cause, by finding the specific mail items, which cause the synchronization problem.
We try to use a couple of tricks (usually turn off and turn on windows), but no luck.