The following steps can aid in the troubleshooting and resolution of Outlook performance issues. These issues can include:

  • Emails stuck in outbox
  • Slow to load email previews
  • Slow to open mailbox folders

Be sure to restart the Outlook app and test whatever was slow after each step.


Steps

Remove Unneeded Items

  1. Click File
  2. Click Tools
  3. Select "Mailbox Cleanup"
  4. Empty the Deleted Items folder by clicking the "Empty" button
  5. Delete alternate/conflicted items by clicking the "Delete" button


Compact Outlook Data File

  1. Click File
  2. Click Account Settings
  3. Click Account Settings
  4. Select the "Data Files" tab
  5. Double-click the data file that you want to compact
  6. Click the "Advanced" tab
  7. Click the "Outlook Data File Settings" button
  8. Click Compact Now
  9. Click OK


Disable Add-ins

  1. Close the Outlook application
  2. Open the Start Menu
  3. Search for "Run"
  4. Type "outlook /safe" in the field and click OK
    • This will open Outlook in Safe mode with no add-ins enabled.
    • You should test emails at this point and see if the issue persists. If the issue is fixed, continue with this section as it is add-in related
  5. Close Outlook and re-open normally
  6. Click File
  7. Click Options
  8. Click the "Add-Ins" tab on the left
  9. Click the "Go" button next to COM Add-Ins at the bottom
  10. Untick all Add-Ins and then the "OK" button
  11. Restart Outlook again
  12. Open the Add-Ins menu again
  13. Enable one add-in and test when was running slowly
  14. Restart Outlook again
    • Systematically enable each add-in one at a time, testing and restarting Outlook between each one until you find the add-in(s) that cause the slowness.
    • Tick all other add-ins and leave the problematic ones unticked


Disable "Download Shared Folders"

  1. Click File
  2. Click Account Settings
  3. Click Account Settings
  4. Stay on the Email tab, double-click the email address having the issues
  5. Click the "More Settings" button
  6. Click the "Advanced" tab
  7. Untick "Download Shared Folders" and click OK
  8. Click the "Next" and "Done" buttons
  9. Restart Outlook


Disable Skype for Business integration

  1. Click File
  2. Click Options
  3. Click the "People" tab on the left
    • This may also be called "Contacts" on certain versions of Outlook
  4. Untick "Display online status next to name"
  5. Click OK


Disable Hardware Graphics Acceleration

  1. Click File
  2. Click Options
  3. Click the "Advanced" tab on the left
  4. Scroll down to the "Display" section
  5. Tick "Disable hardware graphics acceleration"
  6. Click OK


Disable RSS Feeds

  1. Click File
  2. Click Options
  3. Click the "Advanced" tab on the left
  4. Scroll down to the "RSS Feeds" section
  5. Untick "Synchronize RSS Feeds to the Common Feed List"
  6. Click OK


Create new profile

  1. Close Outlook
  2. Open the Start Menu
  3. Search for "Control Panel"
  4. Click on "User Account"
  5. Click on "Mail (Microsoft Outlook) (32-bit)"
  6. Click the "Show Profiles" button
  7. Click the "Add" button
  8. Enter a display name for the profile in the field provided and click the "OK" button
  9. Enter in your email address and password in the fields provided and click the "Next" button
  10. Untick "Set up Outlook Mobile on my phone, too" and click Finish
  11. Change the "Always use this profile" drop-down menu to select the newly created profile and click OK


Repair Office

  1. Close Outlook
  2. Open the Start Menu
  3. Search for "Control Panel"
  4. Click "Uninstall a program"
  5. Scroll down and right-click "Microsoft 365 Apps"
    • This may be called something different depending on what version of Office is installed but is usually something similar to "Microsoft 365 Apps" or "Microsoft Office"
  6. Select "Change"
    • You may be prompted to enter in Admin credentials at this stage
  7. Tick the "Quick Repair" option and click the "Repair" button
    • You will be prompted to close any other Office apps if any are open


Reinstall Office

  1. Download or locate the appropriate Office installer
  2. Close Outlook
  3. Open the Start Menu
  4. Search for "Control Panel"
  5. Click "Uninstall a program"
  6. Scroll down and right-click "Microsoft 365 Apps"
    • This may be called something different depending on what version of Office is installed but is usually something similar to "Microsoft 365 Apps" or "Microsoft Office"
  7. Select "Uninstall"
    • You may be prompted to enter in Admin credentials at this stage
  8. Follow through the prompts to uninstall Office
    • You will be prompted to close any other Office apps if any are open
  9. Run the Office installer and follow the prompts to install the Office apps again
  10. Restart your computer