In certain situations, you may wish to disable the ability for users to modify or add a signature in Outlook, particularly if you manage signatures via Signitic. Here is how to proceed for Outlook Web App (OWA) and Outlook Desktop.
Disable the signature in Outlook Web App (OWA)You can disable the signature feature from the Exchange dashboard:
Open the Exchange Admin Center (EAC).
Go to Roles > Owa web app policies.
Open each relevant policy.
Click on Manage Features.
Under the User Experience section, uncheck "Email signature".
Save the changes.
You can also apply the policy via PowerShell:
Set-OwaMailboxPolicy -Identity "NomDeLaPolitique" -SignaturesEnabled $false
Disable the signature in Outlook DesktopTo disable signatures in Outlook Desktop, you must modify the Windows registry or use the Local Group Policy Editor.
Open Regedit.
Navigate to:
HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Outlook\Options\MailCreate a new DWORD value called disablesignatures.
Set its value to 1.
This will remove the option to create/modify signatures in Outlook Desktop.
If necessary, this link can also assist you on this topic POstponeroamingSignature