Knowledge Base

Troubleshooting the deprecated COM Add-in

Problem:

You experience problems with the CodeTwo Signatures Add-in for Outlook (the COM Add-in), for example you're unable to install or launch it.

The COM Add-in is now deprecated and will be retired by October 2025. We recommend switching to our new Web Add-in to enjoy all the features of the COM Add-in & much more (you will also avoid the problems described in this article). Learn more about the Web Add-in and see how to switch

Solution:

Read on to learn about encountered problems, their causes and recommended solutions.

Add-in installation blocked by Windows Defender Antivirus

When you or your users install the COM Add-in, Windows Defender Antivirus might block the process in the background, which results in a corrupted installation of the add-in. On opening Outlook for Windows, you get the following or similar error (Fig. 1.):

'CodeTwo Signatures Add-in for Outlook' has fired an exception.

The error generated by the improperly installed COM Add-in.
Fig. 1. The error generated by the improperly installed COM Add-in.

When you look closely at Windows Defender Antivirus logs, it turns out the installation is blocked by Attack Surface Reduction (ASR) feature. To solve the problem, you need to temporarily add C:\Windows\System32\rundll32.exe as an exception to the Attack Surface Reduction rule(s) you have in place.

Warning

Adding any exception to the ASR rules might reduce the level of protection they offer. After installing the COM Add-in, we recommend that you remove the exception to maintain your desired level of protection.

Follow the instructions below to add the exception globally by using:

Microsoft Endpoint Manager (Intune)

  1. Follow the instructions outlined here to access your existing endpoint protection profile that includes the ASR rule(s).
  2. Add C:\Windows\System32\rundll32.exe as an exception by pasting it into the text box, as shown in Fig. 2. Click Review + save to save your change.

Adding the exception to ASR rules in Intune.
Fig. 2. Adding the exception to ASR rules in Intune.

  1. Finally, click Save to save your endpoint protection profile.

After the changes propagate across users’ computers, you can try to install the COM Add-in once again.

Group Policy Management Editor (GPO)

  1. Open the Group Policy Management Editor by launching gpmc.msc from the Windows Start menu.
  2. Open the policy covering the ASR rule(s) for editing.
  3. Go to Computer Configuration > Policies > Administrative Templates > Windows Components > Windows Defender Antivirus > Windows Defender Exploit Guard > Attack Surface Reduction and double-click Exclude files and paths from Attack Surface Reduction Rules (Fig. 3.).

Accessing the right ADMX template.
Fig. 3. Accessing the right ADMX template.

  1. In the window that opens, choose Enabled and click the Show button (Fig. 4.).

Opening the pop-up to add the exception.
Fig. 4. Opening the pop-up to add the exception.

  1. Configure the settings in the pop-up (Fig. 5.) as follows:
    • In the Value name field, paste C:\Windows\System32\rundll32.exe.
    • In the Value field, type 0 (zero).
    • Click OK to save the configuration.

Adding the exception.
Fig. 5. Adding the exception.

  1. Finally, click Apply and OK (see Fig. 4.) to close the window and apply the changes.

After the changes propagate across users’ computers, you can try to install the COM Add-in once again.

Tip

You can run the gpupdate /force command to speed up the propagation (press the Windows logo key + R to open the Run box).

Error while checking Outlook version

You get the following or similar error:

It looks like we could not check your Outlook version or Outlook version is not installed on this device.

This error occurs when we are unable to verify which version of Outlook you are using. This may happen if you don't have any Outlook desktop app installed or if your version is too old. Remember that only Outlook 2013 or later is supported. 

If you have an up-to-date version of Outlook but still get this error, the problem might be related to limited access to your system registry. Make sure that the Windows account you are using during the installation has read/write permissions to the following registry key:

Computer\HKEY_CURRENT_USER\Software\Microsoft\Office

Microsoft .NET Framework issues

After you install the CodeTwo Signatures Add-in for Outlook and restart your Outlook desktop app, the add-in crashes and you receive the following error message:

'CodeTwo Signatures Add-in for Outlook' has fired an exception.

that includes the following (or similar) details:

Exception Source: Esig365.Outlook.Addin.Adx
Exception Type: System.IO.FileLoadException
Exception Message: Could not load file or assembly 'Microsoft.Office.Interop.Outlook, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' or one of its dependencies. Access is denied.
Exception Target Site: OnAddinInitialize

This error occurs because of issues related to Microsoft .NET Framework.

To fix it, make sure you have the required .NET Framework version installed on your machine (i.e. Microsoft .NET Framework 4.7.1). If no, download it and perform the update. If necessary, uninstall the current version and then reinstall .NET Framework by running the downloaded installation file.

If this does not solve the problem, download the Microsoft .NET Framework Repair Tool and run it on the affected machine. The tool detects and resolves issues with .NET Framework installations. It should also fix the problem with the add-in as well.

The COM Add-in continuously requires restarting Outlook

The CodeTwo Signatures Add-in for Outlook (COM Add-in) shows a notification that restart is required every time a user changes their default signature in Outlook (provided that you configured your client-side rules to set CodeTwo signatures as the default ones).

If you keep getting this notification repeatedly, it probably means you are using two CodeTwo Outlook add-ins as the same time – the deprecated COM Add-in and the CodeTwo Signatures Web Add-in for Outlook (the modern Web Add-in). The Web Add-in keeps disabling default signatures in Outlook and the COM Add-in tries to set the default signatures on its own.

You can only use either of the CodeTwo Outlook add-ins to avoid conflicts, so we recommend uninstalling the COM Add-in (globally or manually, depending on how it was installed) because it is now deprecated and no longer supported, and it will retire by October 2025.

Learn more about CodeTwo Outlook add-ins

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