Outlook is running slow in Windows 10? Here’s how to fix it

Milan Stanojevic
by Milan Stanojevic
Deputy Editor
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Email is a critical part of our daily lives, whether as individuals or even in business, and for IT admins or managers if emails are down, it can be challenging because it disrupts communication, so it’s their work to get it back up and running.

Outlook is currently the de facto standard email client in the corporate world, which generally works pretty well, but, all this doesn’t come without challenges in its workings.

Among the myriad of issues users face is Outlook running slow in Windows 10 – nothing can be more frustrating than slow speeds, or knowing that everything you do in Outlook will drag.

When Outlook has performance issues, it can be caused either by a corrupt or damaged PST file, an add-in that isn’t functioning, corrupt profile, or a problem with an Outlook application.

However, troubleshooting Outlook running slow in Windows 10 need not be a nightmare for you, as you can use some of the solutions listed below and resume communication normalcy for your business or job (if working remotely).

Note: If you cannot fix Outlook running slow issues or you simply want a good email client, we would strongly recommend Mailbird. A leader on the market, it will satisfy all your needs in mailing management.

How do I fix Outlook slowness on Windows 10?

  1. Open in Safe Mode
  2. Fix Outlook Data File error
  3. Repair the Outlook Profile
  4. Create a new Outlook Profile
  5. Repair Outlook via the Installer
  6. Remove whatever causes the PST to bloat up
  7. Disable RSS feeds
  8. Download complete items
  9. Update Windows
  10. Reduce calendars
  11. Use Cached Exchange Mode
  12. Archive inbox messages
  13. Keep PST file compact
  14. Disable add-ins

1. Open in Safe Mode

  • Hold down the CTRL key when opening Outlook until the message appears. You can also right click Start, select Run, type exe /safe and press Enter
  • If Outlook is slow in Safe Mode, then an Add In could be causing the issue.
  • Click File
  • Select Options
  • Click Add In’s.
  • Scroll down to Manage
  • Click Go, and on the next screen displayed, remove the check marks
  • Disable all add-ins.
  • Start Outlook normally again and see if it works. If so, enable the add-ins one by one until Outlook fails again. The add-in you last enabled is most likely the cause of your issue. Uninstall or reinstall the specific troublesome add-in.

Most Windows users don’t know how easy is to add Safe Mode to the boot menu. Find out how you can do it in just a couple of steps.

Safe mode is not working? Don’t panic, this guide will help you get past the booting problems.

2. Fix Data File errors

If disabling Add Ins in Outlook while in Safe Mode, does not resolve the performance issues, it is most likely that a corrupted PST file or profile is causing the issue.

The PST or personal storage folder, also known as a .pst file is where Outlook stores messages, contacts, appointments, tasks, notes, and journal entries

  • Click Control Panel and select Mail to find the PST file
  • Click the Data Files
  • If there is more than one PST file, look for the one with the checkmark (default)
  • Go to the path shown in the Data Files window, e.g. C:UsersstellaxxxxxAppDataLocalMicrosoftOutlook
  • Go to Show hidden files, folders and drives and uncheck Hide extensions for known file types
  • Save a backup copy of the PST file to safe location or removable storage
  • Rename the .pst extension to .psp
  • Open Outlook again
  • Click OK twice when prompted during start up to create a new PST file. If Outlook opens successfully and there are no performance issues, then the original PST file is the problem. If however, the new generic PST file shows the same issues, then either it is a corrupt profile or Outlook is damaged. In which case, repair your Outlook profile (described in the next solution)
  • Rename the .psp file back to .pst
  • Run the scanpst.exe tool on the original file and test. Outlook shouldn’t be running for this process.
  • Try opening Outlook again

If you want to open hidden file in Windows 10, follow the simple steps from this guide.

You can’t open Control Panel? Take a look at this step-by-step guide to find a solution.

3. Repair the Outlook Profile

If you find Outlook running slow in Windows 10 with a generic PST file, then it probably has a corrupted profile which you can try to repair from the Control Panel. To do this:

  • Open Control Panel
  • Select Mail
  • Click on E-mail Accounts
  • In the Account Settings dialog box, go to E-mail tab
  • Highlight your account, and click Repair, then follow any prompts from the repair wizard
  • Click Finish
  • When the repair is done, restart Outlook

You can also copy the existing profile and see if it opens:

  • Open Control Panel
  • Select Mail
  • Click Show Profiles
  • Click Copy
  • Enter a new name for the profile i.e. add a 1 at the end
  • Select your new profile from the drop down box, below the “Always use this profile” radio button
  • Click OK.
  • Restart Outlook.

If there is still a problem, try the next solution.

Your Outlook profile is corrupted? Take a look at this article and learn how to repair it in no time.

4. Create a new Outlook Profile

If you still find Outlook running slow in Windows 10, and the copy and repair functions failed, try creating a new profile.

  • Open Control Panel
  • Select Mail
  • Click Show Profiles
  • Click Add, enter the name of the new profile
  • Select Prompt for a profile to be used then click OK
  • Start Outlook, and select the new profile. If the it allows Outlook to perform normally, you can move your data across to the new profile

5. Repair Outlook via the Installer

If none of the above steps worked, then your Outlook is probably damaged. You can repair Outlook by choosing Change in Apps and features (right click Start and select Apps and Features).

If this and the other methods above fail, you have to uninstall and reinstall Outlook/Office.

Need more info on how to repair Outlook on Windows 10? Check out this useful guide.

6. Remove whatever causes the PST to bloat up

When Outlook is running slow in Windows 10, it could be because of the piled up documents, notes, calendar entries and attachments, among other files in the Outlook PST, which make it too large in size, so it starts dragging in terms of speed and performance.

In this case, you need to offload the PST file, by doing the following:

  • Find a folder called Larger than 100 Kb
  • Delete all unwanted old emails (with bulky attachments). Save attachments you need to the disk but remove them from the PST.
  • Delete all other unwanted emails
  • Clear out the Trash.
  • Archive your emails by year to relieve the PST file

7. Disable RSS feeds

Outlook syncs RSS feeds from Internet Explorer by default, to its RSS reader, so if you have many bookmarked feeds, the syncing could slow down Outlook.

Go to Options>Advanced and disable this feature by unchecking both options under the RSS feeds.

8. Download complete items

Outlook should be set up to download full and complete messages when connected with IMAP or POP3, so that it doesn’t have to sync with the server each time you click on a new email or item.

Look for the Download Complete Item Including Attachments setting to enable this.

9. Update Windows

Windows Updates for Office are also ‘hidden’ so you need to allow these to install because sometimes Microsoft updates Exchange, and this can break or cause issues with the Outlook-Exchange communication.

Check also for patches issued by Microsoft for Outlook to resolve speed issues or other problems.

If you can’t open the Setting app, take a look at this article to solve the issue.

Having trouble updating your Windows? Check out this guide that will help you solve them in no time.

10. Reduce calendars

Outlook running slow in Windows 10 can be worsened by more data, which Outlook is forced to pull from the Internet, so it drags. You can have one or two shared calendars, but more data means a sluggish Outlook.

11. Use Cached Exchange Mode

This takes the data file from the PST and caches it on your OST, hence speeding up Outlook as it won’t have to read its data file via a network, but through a locally stored data file.

However, you can only enable this option when connecting Outlook with Exchange server.

12. Archive inbox messages

Millions of email users, including Outlook, have thousands of emails – usually unread – in their inbox, which can cause serious problems when using PST files. You can set up auto-archiving so that the Inbox only retains some of those many emails.

Keep current and previous months’ emails in your Inbox folder, and the rest of them, just archive. This creates a new data file, which relieves Outlook of having to strain from an oversized PST/OST file.

13. Keep PST file compact

If the PST file goes overboard, you can use a tool to keep it under control. To do this:

  • Go to Account Settings
  • Click Data files
  • Select the data you want to compact
  • Click Settings
  • Select Advanced
  • Click Outlook Data File settings
  • Click Compact Now

14. Disable add-ins

Any add-ins can slow down Outlook. Here’s how to find out add-ins installed in Outlook:

  • Open Outlook
  • Go to Options
  • Click Add-ins
  • Select COM add-ins from the drop down
  • Click Go, which displays the list of all available Outlook add-ins
  • Find the suspect add-ins and uncheck their corresponding boxes

Were you able to fix Outlook running slow in Windows 10 using the solutions above? Let us know in the comments section below.


Editor’s Note: This post was originally published in April 2018 and has been since completely revamped and updated for freshness, accuracy, and comprehensiveness.