Hi @Admin Muskaan Muskaan ,
You can use DisableSignature registry key to prevent users from adding or editing signatures in Outlook. Moreover, users can still use the existing signature.
(Important Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.)
The registry should be located at: Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\MailSettings
Click Edit > New > DWORD. Type a name DisableSignature and set the value to 1.
Here is an article for your reference: How to: Disable End-User's Ability to Add, Edit, & Remove Outlook Signatures
(Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)
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