Microsoft provides third-party contact information to help you find additional information about this topic. You can reference this website: How to delete OWA (Outlook on the web) signatures in Microsoft Exchange Opens a new window to remove signature. Mind that unless you disable adding email signatures in OWA, users can create such signatures again, after you delete them. It is especially useful if you manage your email signatures centrally and want to avoid double signatures from users who use OWA as their email client. The email signature is deleted from the target users' OWA settings, so that this client will no longer add those email signatures automatically and a user will not be able to add the OWA signature manually, using the built-in option. Using Windows PowerShell, you can delete a client-side signature from OWA from any user in your organization.