When using the term “Exchange Mailbox”, we are using an “alias” for a Database that hosted on the Exchange server. Instead of “fetching” the mail from the remote Mailbox, each time a user click on the mail item. Using a local copy of the Mailbox content should significantly improve the Outlook performance (response time) because access to the “data” (Mail items) created by using a local copy of the Mailbox that stored on the local drive. The meaning of “cache mode” is that Outlook client, will try to download all the Mailboxes content from the Exchange server to the local hard drive and save the information in a local Database (OST File). Part 1: Introduction Outlook Cache mode and the OST Databaseīy default, Outlook client is configured with the option of cache mode. So, in case that this is your scenario, the only advice that I can offer is: Be patient and read the information. I know that this article could consider as “long and tedious” but the Murphy law dictates that: most of the Outlook synchronization problem accrues to “VIP Users,” In this article, we review the cases and the troubleshooting steps for mitigating optional causes for Outlook synchronization problems in Office 365 environment and review the specific charters of Outlook and Exchange Online environment. The less good news is that there are many grounds for this issue, and there is no “magic” solution that will help us to solve the synchronization problem in “one click.”

The good news is that we can solve this problem.

Each time we open Outlook, the synchronization process start and stop in the middle, for some reason, we cannot figure. We try to use a couple of tricks (usually turn off and turn on windows), but no luck. One of our users complains that he cannot synchronize mail from his Mailbox in the cloud (Exchange Online).

Outlook 2016 sync issues 0x80004005