Troubleshooting Outlook Performance Issues

Summary

This guide helps you troubleshoot and resolve: Troubleshooting Outlook Performance Issues. Follow the steps below to fix the issue.

Common Causes

Common Symptoms

• Outlook takes a long time to start or open.
• Typing is slow or laggy.
• Programme freezes or crashes frequently (not responding).
• Searching is very slow.
• High CPU or memory usage in Task Manager.

Step‑by‑Step Troubleshooting

1. Check for Updates

Ensure Outlook is fully updated, as performance fixes are often released in updates. See How to update Windows for guidance.

• Go to File > Office Account > Update Options > Update Now.

2. Disable Add‑ins (Most Common Cause)

Third‑party add‑ins (e.g., Teams, Zoom, Adobe, Dropbox, antivirus integration) are frequent causes of slowness.

• Go to File > Options > Add‑ins.
• At the bottom, next to “Manage:”, select COM Add‑ins and click Go….
• Uncheck all non‑essential add‑ins.
• Click OK and restart Outlook.
• If Outlook is fast, re‑enable add‑ins one by one to identify the culprit.

3. Reduce Data File Size and Cache

Large PST/OST files and an oversized cache can cause significant slowdowns.

• Locate your data file: File > Account Settings > Account Settings > Data Files.
• Select the file and click Settings.
• If it is a PST file, click Compact Now. Ensure you have at least 10 % of the file size free on the drive.
• If it is an OST file, reduce the amount of mail kept offline:

• Go to File > Account Settings > Account Settings.
• Double‑click your email account.
• Under “Mail to keep offline”, move the slider to a shorter timeframe (e.g., 3 or 6 months) instead of “All”.
• Click Next > Finish > Restart Outlook to create a smaller OST file.

4. Run Outlook in Safe Mode

Safe Mode opens Outlook without add‑ins and extensions, helping confirm whether they are the issue.

• Close Outlook.
• Press Win + R, type outlook /safe, and press Enter.
• If Outlook runs normally, an add‑in or corrupted settings file is likely the cause.

5. Disable Hardware Graphics Acceleration

Graphics rendering conflicts can affect Outlook performance.

• Go to File > Options > Advanced.
• Scroll to the Display section.
• Check “Disable hardware graphics acceleration”.
• Click OK and restart Outlook. (In newer versions, also found under File > Options > General > Disable animated controls and animations.)

6. Optimise Outlook Search Index

Rebuilding the Outlook search index is preferred to excluding the data folder.

• Open Control Panel > Indexing Options.
• Click Modify, ensure Microsoft Outlook is selected, then click OK.
• Back in the Indexing Options window, click Advanced and under the Index Settings tab, click Rebuild. This may take some time.

7. Repair Office (Quick or Online Repair)

If Outlook files are corrupted, repair the Office installation.

• Open Settings > Apps > Installed Apps (or Apps & Features).
• Find Microsoft Office, click Modify (or the three‑dot menu > Modify).
• Select Quick Repair. If the issue persists, run Online Repair.
• Restart the computer after the repair completes.

8. Scan PST/OST with the Inbox Repair Tool

Use the built‑in ScanPST utility to repair corrupted data files.

• Locate SCANPST.EXE (usually in C:\Program Files\Microsoft Office\root\Office16).
• Close Outlook, run the tool, and follow the prompts to repair the file.

9. Check for Malware

Run a full scan with Windows Security or your organisation’s antivirus to ensure no malware is interfering with system resources.

10. Create a New Outlook Profile

A corrupted profile can cause crashes and slowness.

• Close Outlook.
• Open Control Panel and search for Mail (32‑bit).
• Click Show Profiles.
• Click Add…, give the profile a name (e.g., “Outlook Test”), and set up the email account again.
• Select “Prompt for a profile to be used”, restart Outlook, and choose the new profile. If it works, set it as the default.

11. Additional Optimisation Steps

• Check Antivirus Exclusions: Ensure your antivirus excludes OST/PST files and outlook.exe from real‑time scanning.
• Disable Roaming Cache: In corporate environments with roaming profiles, large cache files can slow logins and Outlook. Adjust cache settings via Group Policy or the Outlook client.
• Clear Cached Mode Data: In File > Account Settings > Account Settings > Data Files, select the OST and click Clear Offline Items, then let Outlook resynchronise.
• Reset the Navigation Pane: Run outlook.exe /resetnavpane from the Run dialog.
• Check Mailbox Size: In Outlook, go to File > Tools > Mailbox Cleanup > View Mailbox Size and archive or delete old items as needed.

When to Seek Further Assistance

If you have tried the steps above (especially creating a new profile) and the issue persists, it may indicate a deeper hardware problem, operating system corruption, or a complex Exchange connectivity issue. Open a Ticket for further support.

Still Having Issues?