How to fix Microsoft Outlook 'Trying to Connect' or stuck on connecting to server status

Summary

This guide helps you troubleshoot and resolve: How to fix Microsoft Outlook 'Trying to Connect' or stuck on connecting to server status. Follow the steps below to fix the issue.

Common Causes

When the Outlook desktop application displays "Trying to Connect" or remains stuck on a connecting status, it usually means Outlook cannot communicate with the Microsoft 365 Exchange server. This is commonly caused by outdated software, corrupted Outlook profiles, cached credentials, or local network issues. The steps below will walk you through resolving the problem, starting with the quickest fixes and moving to more detailed troubleshooting.

Quick Fix Steps

Before diving into detailed troubleshooting, try these common fixes first. Most connection issues are resolved by completing these steps in order.

1. Check your internet connection. Open a web browser and visit any website to confirm your network is working. If other devices on the same network are also offline, the issue is with your internet service rather than Outlook.
2. Restart Outlook. Close Outlook completely, wait ten seconds, then reopen it. On Windows, check the system tray (near the clock) and right-click the Outlook icon to select Quit if it is still running.
3. Restart your computer. A full restart clears temporary glitches that can prevent Outlook from connecting.
4. Check the Microsoft 365 service status. Visit Microsoft 365 Service Status in your browser to confirm there are no active outages affecting Exchange Online.
5. Update Outlook. An outdated version can cause connection problems. In Outlook, go to File > Office Account > Update Options > Update Now.

If Outlook is still stuck after completing the quick fixes, continue to the detailed instructions below.

Detailed Instructions

Run Outlook in Safe Mode

Starting Outlook in Safe Mode disables add-ins and customisations that may be interfering with the connection. This is a useful diagnostic step to determine whether an add-in is the cause.

1. Close Outlook completely.
2. Press and hold Ctrl on your keyboard, then double-click the Outlook shortcut or run outlook.exe /safe from the Run dialog (Windows + R).
3. If Outlook connects normally in Safe Mode, an add-in is likely the cause. Disable add-ins one at a time via File > Options > Add-ins to identify the culprit.

Repair Your Outlook Profile

A corrupted profile can prevent Outlook from authenticating with the Exchange server. Outlook includes a built-in repair tool that can fix common profile issues.

1. Open the Control Panel and search for Mail (Microsoft Outlook).
2. Click Show Profiles, select your profile, then click Properties.
3. Click Email Accounts, select your Microsoft 365 account, then click Repair.
4. Follow the prompts to complete the repair process, then restart Outlook.

Clear Cached Credentials

Outlook stores authentication credentials in the Windows Credential Manager. If these credentials are outdated or corrupted, Outlook will fail to connect.

1. Close Outlook.
2. Open Credential Manager by searching for it in the Start menu.
3. Click Windows Credentials.
4. Remove any entries related to outlook.office365.com, microsoftonline, or MicrosoftOffice16.
5. Restart Outlook and sign in again when prompted. Outlook will create fresh credentials.

Recreate the Outlook Data File

Outlook uses an Offline Outlook Data File (.ost) to cache your mailbox. If this file becomes corrupted, Outlook may get stuck trying to connect. Recreating the file forces Outlook to download a fresh copy from the server.

1. Close Outlook.
2. Press Windows + R, type %localappdata%\Microsoft\Outlook, and press Enter.
3. Locate the .ost file matching your email address and rename it by adding .old to the end of the filename.
4. Restart Outlook. A new .ost file will be created automatically and your mailbox will resynchronise.

Troubleshooting

If the steps above have not resolved the issue, work through the following additional checks.

Verify DNS Settings

Incorrect DNS settings can prevent Outlook from locating the Exchange server. Confirm your computer is using a valid DNS server.

1. Open Command Prompt and run nslookup outlook.office365.com.
2. If the command returns an IP address, your DNS is working correctly.
3. If it fails or times out, try changing your DNS servers to 1.1.1.1 and 1.0.0.1 (Cloudflare) or 8.8.8.8 and 8.8.4.4 (Google) in your network adapter settings.

Check Firewall and Antivirus Software

Security software can sometimes block Outlook's connection to the Exchange server, particularly after updates.

• Temporarily disable third-party antivirus or firewall software and test Outlook.
• If Outlook connects with the software disabled, add an exception for Outlook.exe in your security application.
• Ensure your firewall allows traffic on ports 443 (HTTPS) and 587 (SMTP submission).

Test with a New Outlook Profile

Creating a fresh profile rules out profile-level corruption that the repair tool may not fix.

1. Open Control Panel > Mail (Microsoft Outlook) > Show Profiles.
2. Click Add, enter a name for the new profile, and follow the prompts to add your email account.
3. Set the new profile as the default and restart Outlook.

Check Proxy Settings

If your organisation uses a proxy server, misconfigured proxy settings in Windows can block Outlook's connection.

1. Open Settings > Network & Internet > Proxy.
2. Review the proxy configuration. If you do not use a proxy, ensure Automatically detect settings is on and manual proxy entries are turned off.
3. Restart Outlook after making changes.

Related Articles

• Setting Up an Email Account in Outlook (POP/IMAP/Exchange)
• Troubleshooting Outlook Send/Receive Errors
• Backing Up and Restoring Outlook Data Files (.pst/.ost)

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