How to speed up Outlook with Exchange 2010/2013 - DISABLE Cached Exchange Mode

1. Outlook 2010 and 2013 have a feature called Cached Exchange Mode that keeps a copy of your email on your computer. The copy is faster for Outlook to load and search, and you can access it when your computer is not connected to the Internet.

Outlook 2013 for Windows lets you choose how much email to keep in the cache. By default, it stores email for up to twelve months on your machine and tries to keep track that all folders are in syc. 

To make Outlook faster, Disable this feature

1. Click File > Account Settings > Account Settings
2. In the Account Settings window, double-click your Microsoft Exchange account on the E-mail tab
3. In the Change Account window, drag the Mail to keep offline slider to the desired number of months to zero.
4. Click Next and then Finish

For more information, see the Microsoft Support article Only a subset of your Exchange mailbox items are synchronized in Outlook 2013.

2. Make sure that the critical folders (Inbox, Sent, Deleted, Drafts) have no more than 5,000 messages in them. Outlook performance decreases significantly when there are more than 5,000 messages in any of those folders.

If you have larger than 5000 emails in any of these folders, simply create subfolders and drag old messages there.

Once you do the above, make sure to give outlook some time to sync these emails into the folders and you will see a major boost in speed.

We also suggest checking that there are no any unnecessary add-ons running in Outlook that may be causing this delay. To check for this in Outlook go to 

File>Options>Add-ins. Under Active Application Add-Ins I suggest you search for and disable any add-ins that refer to your installed anti-virus software. Sometimes anti-virus add-ins can interfere with sending/receiving in Outlook.