Outlook Sync Troubleshooting Guide

The following guide will run through a few of the Common issues with Outlook sync and other Outlook issues.

Check if New Outlook is Enabled

New Outlook does not store any local data and is just a Web Frame to Office Online, even if you are using POP or IMAP folders. If you are using an Exchange type account we can link directly to Exchange, but if not, we recommending switching back to Classic Outlook.

Click Here for our guide on Turning Off New Outlook.

How to Install Classic Outlook for Windows

Watch this video to see how install Classic Outlook.

If you only have access to "New" Outlook or the free newly branded New Outlook (Formerly Windows Mail), you can install the Classic version of Office from Microsoft's Website.

There are 2 types of installers, online and offline. The online installer is easier and usually works, but not always, when the online installer does not install Classic Outlook, you must use the offline installer.

1. Online Installer (Easiest method)

Click Here to download the Classic Outlook online Installer.
Follow the Install Prompts
Connect Your Email Accounts
Setup CompanionLink.

Note: If this does not install Classic Outlook, you must use the offline installer:

2. Offline Installer (Most Reliable)

Click Here to download the Classic Outlook offline Installer.
Right click the IMG file > Mount
Click Open if prompted
In the mounted directory, Go to the Office Folder and run Setup64.exe
Follow the Install Prompts
Connect Your Email Accounts
Setup CompanionLink.

Incorrect Data Syncs

If the sync is working, but incorrect information is appearing on the device, you most likely have an incorrect set of Outlook Folders selected. To change the Outlook Folders you are syncing with:

1. Open CompanionLink

2. Click Settings on the left

3. Click Advanced in the bottom left

4. Click the Outlook Folders tab at the top.

5. Check the drop down for each data type, if you see multiple folders, you might have the wrong one selected.

After changing the Outlook Folders, if you have already synced once with the device, you will want to preform a Wipe Sync after changing the folders. Otherwise it could mix the incorrect information with the correct information.

Use the following guide to enable a Wipe. Preforming a Wipe Sync

Invalid Class String\Server Execution Failed\No Default Mail Client

If you receive an Invalid Class String, Server Execution Failed or No Default Mail Client message when syncing, the first step is running a quick repair of Outlook.

Please use the following guide to run a quick repair of Outlook. Quick Repairing Outlook

If the error still occurs, we will need to disable two files in the CompanionLink folder.

You can achieve this automatically through CompanionLink settings:

1. Open CompanionLink

2. On your keyboard hit the key combination CTRL + SHIFT + U

3. In the window that opens, check the option "Disable MAPI", then click OK to save.

Or manually by renaming the two files:

1. Open the file explorer of Windows and navigate to C:\Program Files (x86)\CompanionLink.

2. Click the View in the top of the file explorer and on the right enable "File Name Extensions" if it is not already enabled.

3. Now in the folder below, find "ClxMapi64.exe" and "ClxMapi.dll". Rename these files "ClxMapi.dll.old" and "ClxMapi64.exe.old".

4. (Optional) Click the "File Name Extensions" options again to disable the extensions showing.

Once the MAPIs are disabled, restart the machine and try running the sync again.

If that does not work try doing a "Send/Receive All Folders" in Outlook, this can be done in the Send/Receive tab > click Send/Receive All Folders, after the Send/Receive is complete, restart the machine and try the sync again.

Outlook closes when you sync

If Outlook is closing on a sync, CompanionLink or Outlook is most likely running in an elevated permission level. Use these steps to ensure neither are set to a higher level:

1. On the desktop of the PC, find and right click on the icon for Outlook.

Note: If you right click on it from the Taskbar, you will need to right click on the name of the program and again to see the properties option.

2. Select Properties

3. Find the Compatibility tab.

Note: If Outlook does not have a Compatibility tab, find the Shortcut tab at the top and select Advanced towards the bottom.

4. Ensure the option to "Run As Administrator" is unchecked.

5. Repeat this same check for the CompanionLink icon.

Select your Outlook Profile appears on each sync

Outlook can use multiple Profiles. Each profile is completely separate from each other. If you only use one Outlook profile that you are aware of, use the following steps to set it as the "Default" so Outlook will not prompt each time.

1. Open the Control Panel of Windows

2. Select the Mail option. (It might show Mail followed by your version of Outlook or Mail and 32\64bit)

Note: If you do not see the Mail option, in the top right of the Control Panel change View By to Small or Large Icons.

3. Select Show Profiles

4. Towards the bottom select Always Use This Profile. Your current profile will likely be already selected here.

5. Click Apply and Ok.

When you reopen Outlook you should no longer be prompted to select a profile. This will allow CompanionLink to also sync without this profile selection windows opening.

Note: These steps can also resolve the error message that a different Outlook is currently open than the one desired. Make sure that the profile selected under Always Use This Profile is also selected on the Outlook profiles tab in CompanionLink Advanced Settings.

Please Re-select Outlook folders

If you change your default data files or add new ones in Outlook, you may see this error appear the next time you try to sync via CompanionLink. Verifying your folders will refresh the CompanionLink configuration and correct the error.

Open CompanionLink
Click Settings on the left
Click Advanced in the bottom left
Click the Outlook Folders tab at the top.
Click the drop down for each data type, ensure you have the correct folder selected, and click OK to save the settings.

After re-selecting all of your folders, try syncing again.

A program is trying to access e-mail addresses you have stored in Outlook

If you receive a prompt about Allowing Access with a drop down for a select time, Outlook's older Trust Center Settings are likely interfering with your current Antivirus program.

Use the following guide to stop this prompt from appearing. Fixing the Always Allow Prompt

Other Sync Errors and Issues

If you receive any other errors relating to the sync to Outlook, please try these steps

Please use the following guide to run a quick repair of Outlook. Quick Repairing Outlook
Use the following guide to run a ScanPST or ScanOST on your Outlook data file. ScanPST or ScanOST Instructions
Verify your Outlook Folders in CompanionLink > Settings > Advanced (bottom left) > Outlook Folders tab, ensure the correct folders are selected and the record counts make sense. If the record counts are wrong, try doing the steps below:

If the error still occurs, we will need to disable two files in the CompanionLink folder.

You can achieve this automatically through CompanionLink settings:

1. Open CompanionLink

2. On your keyboard hit the key combination CTRL + SHIFT + U

3. In the window that opens, check the option "Disable MAPI", then click OK to save.

Or manually by renaming the two files:

1. Open the file explorer of Windows and navigate to C:\Program Files (x86)\CompanionLink.

2. Click the View in the top of the file explorer and on the right enable "File Name Extensions" if it is not already enabled.

3. Now in the folder below, find "ClxMapi64.exe" and "ClxMapi.dll". Rename these files "ClxMapi.dll.old" and "ClxMapi64.exe.old".

4. (Optional) Click the "File Name Extensions" options again to disable the extensions showing.

Once the MAPIs are disabled, restart the machine and try running the sync again.

If that does not work try doing a "Send/Receive All Folders" in Outlook, this can be done in the Send/Receive tab > click Send/Receive All Folders, after the Send/Receive is complete, restart the machine and try the sync again.

If you are still having issues, please contact our Technical Support for further assistance.

Usability Issues in Outlook

‘can’t connect to server’ When Creating a Group

When using classic Outlook to create groups, the Create Group window opens and after you fill out the required information, you get a red error message: "Can't connect to the server" below the Name field.
Currently this is not fixed yet according to Microsoft.
This is the workaround provided by Microsoft:

To work around the issue, create and edit groups using Outlook Web Access (OWA) or new Outlook.

Gmail Google Email Sync Failure

Users may encounter errors 0x800CCC0E or 0x800CCC0F.

This issue been fixed by an update on March 20th 2026. There should be no change needed on your end however you may need to update Outlook in Outlook > File > Office Account > Update Options > Update Now. There is more information on the link.

Yahoo Email Sync Failure

Users may encounter errors 0x800CCC0E or 0x800CCC0F.

This issue been fixed by an update on March 20th 2026. There should be no change needed on your end however you may need to update Outlook in Outlook > File > Office Account > Update Options > Update Now. There is more information on the link.

Outlook Freezing and Crashing

There was an issue in early 2026 with Outlook freezing and sometimes crashing when doing normal contact and calendar management. This was caused by a Windows update and has been fixed by a subsequent update. You can update Windows using the following steps:

Right-click the Windows Start button (Windows icon in the taskbar) and select Settings.
Select Windows Update on Windows 11, or on Windows 10 select Update & Security.
Select Install Now and restart as appropriate until Windows Update shows “You’re up to date”.

Classic Outlook crashes and opens in Safe Mode

Outlook closes and a start in safe mode prompt appears

This is caused by an incompatibility with older versions of Outlook and the new Teams add-in in Outlook. Microsoft will not be providing a proper fix for this. If you are able to update Outlook, that would be the fix (Outlook > File > Office Account > Update Options > Update Now) however if your license does not cover a newer version of Outlook, if you do not want to purchase a newer version of Outlook the only solution is to remove the Teams add-in. This can be done in Outlook > File > Options > COM Add-ins > Manage COM Add-ins > Go > Find the Teams Add-in and uncheck it.

Templates Missing From Outlook

When you write an email you find that in My Templates, the View Templates button is missing from the ribbon in classic Outlook.
If you select All Apps on the ribbon, My Templates is missing there as well.
If you try to add the add-in back, you get an error "Something went wrong".

Microsoft is currently investigating this issue and has not provided a fix yet.

This is not a Valid Style Name Error

When you start a new email, view an existing email, or reply to an email you may see the error message:
The error occurs when Outlook is rendering the signature. In addition, you may see the signature in the email now has a
tag inserted.

There is a fix for this issue however you will need to delete any effected email signatures and recreate them. The fix is simply to update Outlook in Outlook > File > Office Account > Update Options > Update Now

Can't Connect to Server when creating a Group

When using classic Outlook to create groups, the Create Group window opens and after you fill out the required information, you get a red error message: "Can't connect to the server" below the Name field.
An internal server error occurred. The operation failed. Both AAD and MSGraph clients are null or AAD Graph is disabled for this API.

Microsoft is investigating this issue with no fix yet.