Exchange Online

If users are experiencing slowness when using Outlook after migrating to Exchange Online, check if Cached Exchange Mode is disabled in Outlook.  Cached Exchange Mode enables a better experience when you use an Exchange account.  In this mode, a copy of your mailbox is saved on your computer.  This copy provides quick access to your data, and it is frequently updated with the server that runs Microsoft Exchange.

1. Click File > Account Settings > Account Settings.

2. Click the Exchange or Office 365 account, and then click Change.

3. Under Offline Settings, check Use Cached Exchange Mode.

4. Exit, and then restart Outlook.

Please note, if the user is connecting to over 500 folders, Cached Exchange Mode may not be appropriate.  Please see the topic, 500 Folder Limit in Outlook, for more information.    

Outlook for Windows has a limit of 500 shared folders.  This limit has been in place since cached mode was introduced in 2003.  Users running cached mode while attempting to access over 500 folders experience performance and synchronization problems.  While running Exchange on-premises, the recommended action for users with access to over 500 folders was to disable cached mode.  With Exchange Online, cached mode offers a much better experience.  However, if users need access to over 500 folders, running online mode (cached mode disabled) may be required, but will likely result in Outlook feeling slow.  For users with access to over 500 folders, the following options are available:

1. Disabled Cached Exchange Mode
   • This will prevent synchronization issues, however the user will still experience performance issues (latency).
2. Move the user to the Office 365 ProPlus 
   • The Office 365 ProPlus is a version of Office that is available through Office 365. 
   • The latest general release of Office 365 version (Version 1908, January 14, 2020) includes support for synchronizing more than 500 folders in Outlook.
   • If the user also uses Project or Visio, this solution is not currently viable as installing Office 365 requires uninstall of all Office msi files.  A solution to install Office 365 along with additional offerings such as Project or Visio will be available shortly. 
3. Have the user use Outlook on the Web instead of the desktop application
   • Outlook on the Web is closer to feature parity to the desktop application than the previously used Outlook Web App
   • Go to https://outlook.office365.com to access Outlook on the Web
4. Have the user reduce folders to under 500
   • The total number of folders including shared mailboxes and archives would need to be reduced to under 500. 

Additional Resources from Microsoft:

• Performance and synchronization problems when you work with folders in a secondary mailbox in Outlook: https://support.microsoft.com/en-us/help/3115602/performance-and-synchro...
• Lifting the 500 Folder Limit in Outlook: https://blog-insider.office.com/2019/06/04/lifting-the-500-folder-limit-...
• Release notes for Semi-Annual Channel releases in 2020: https://docs.microsoft.com/en-us/officeupdates/semi-annual-channel-2020#...

Distribution lists are currently remaining on premises.  While distribution lists are on premises, users who have migrated to Exchange Online will not have the ability to manage their own distribution lists using Outlook or Outlook on the Web.  Group membership can be managed through Active Directory.

Archive and retention policies do not migrate to Exchange Online.  The default policy in Exchange Online is set to never archive, ensuing users will not have unexpected archiving of email. Users will be able to re-establish policies of their choice once they have migrated to Exchange Online. 

Exchange Online forces a 30 day retention policy on the Junk email folder.  Any email stored in the Junk folder will be deleted automatically after 30 days.

There are limitations on shared calendars, Send As, and Send on Behalf functionality between accounts that have migrated to Exchange Online and those yet to migrate.  Migrations will be completed by department to help reduce these known limitations.  The limitations will resolve as Exchange resources migrate to Exchange Online. 

Shared calendars between migrated and non-migrated Exchange accounts may not function as expected.  Non-migrated Exchange users may have limited ability to see the full details of a shared calendar for users/resources that have been migrated, instead seeing only free/busy information.  Accounts that have been migrated will be able to interact with non-migrated accounts. 

calendar_freebusyinformation.png

A majority of users will need to re-configure email on their mobile device after migrating to Exchange Online.  Resources are available under Device Setup. 

Users may get the duplicate folder Archive1 if you had an existing Archive folder. If newly archived email is being moved to the Archive1 folder, follow the steps provided by Microsoft:

https://support.microsoft.com/en-us/help/4010182/archive-folder-is-automatically-added-to-your-office-365-mailbox

Access and permissions to items like shared calendars can take time to resolve on the day after the migration to Exchange Online.  In most cases, these issues will resolve themselves in the first half of the day after the migration.  If user are having issues accessing a shared resource after the migration, please let the Exchange Online Migration team know. The team will verify the resource and permissions have migrated successfully and monitor the issue until it has been resolved. 

Please see the FAQs page for users that addressed frequently asked questions about the migration including solutions and instructions for known issues listed below.