Scenario
You have installed Exclaimer - Signatures for Microsoft 365, but some of your users still have a signature applied directly by Microsoft Outlook.
You want to disable their existing Outlook signatures and prevent them from setting up signatures in Microsoft Outlook in future.
Resolution
You can disable Microsoft Outlook signatures by creating a Configuration Policy in Microsoft Endpoint Manager (Intune) or using Group Policy.
This will make all the Outlook e-mail signature settings unavailable to users. They will not be able to add, delete, edit signatures or change the default signature settings.
In some versions of Outlook, the Signature button is also removed from the ribbon bar in the New message window.
You can combine this setting with a script to remove all existing signatures. If you would like more information, please see: How to delete existing signatures from Microsoft Outlook (Windows).
The machine must be Azure AD-joined, and the user must be signed in with their Azure AD account.
Pre-requisites for Group Policy
The machine must be domain-joined (on-premises), and the user must sign in with their domain user account.
Download and extract Administrative Template files (ADMX/ADML) for Microsoft 365 Apps for enterprise/Office LTSC 2021/Office 2019/Office 2016
https://www.microsoft.com/en-us/download/details.aspx?id=49030
ADMX files should be extracted to C:\Windows\PolicyDefinitions or your central store folder if you have configured one. For more information about configuring a central store, see https://learn.microsoft.com/en-us/troubleshoot/windows-client/group-policy/create-and-manage-central-store.
ADML files should be exported to the appropriate language-specific subfolder within the PolicyDefinitions folder. Example: C:\Windows\PolicyDefinitions\en-US
Please click on the required options listed below to go through the detailed description:
- Browse to the Microsoft Endpoint Manager and sign in.
- Click Devices, then click Configuration Profiles.
- Click Create profile.
Example:
The Create a profile window is displayed.
- Select the most appropriate Windows platform.
- For profile type, select Settings Catalog.
- In Name the profile, enter a meaningful name; for example: Disable Signatures.
- Click Next.
- Click Add settings.
- Scroll down to, and expand, Microsoft Outlook 2016 (this setting works for Outlook 2016 and above).
- Select Outlook Options.
- Select Mail Format.
- In the Settings picker, tick the option Do not allow signatures for e-mail messages (User).
Example:
- Enable the option Do not allow signatures for e-mail messages (User).
Example:
- Click Next.
- (Optional) Add Scope tags as required.
- Click Next.
- Click Add groups and specify a group in Azure or click Add all users to include the required users in this profile.
- Click Next.
- Review the settings, then click Create
- Select the required domain.
- Open Group Policy Management
- Either click on the Action menu and select Create a GPO in this domain>Link it here…or right-click the required domain and select Create a GPO in this domain>Link it here…
The example screen displays the right-click menu:
The New GPO window is displayed.
- Specify a name for the new Group Policy Object (GPO) and click OK.
- Right-click the newly created GPO and click Edit.
- Navigate to Users Administrative Templates by expanding User Configuration>Policies>Administrative Templates:
- Expand Microsoft Outlook 2016 > Outlook Options > Mail Format.
- On the right-hand side, enable the Do not allow signatures for e-mail messages policy to disable the signatures in Microsoft Outlook 2013 (or Microsoft Outlook 2016):
NOTE: Signature options will be disabled, and these changes will prevent signatures in Outlook from being applied. However, the existing signature files will not be deleted from client computers – this should either be done manually or using a script.