Server-Side Email Signature
An email signature applied to outgoing email at the mail server before delivery, ensuring consistency across every device and client the sender uses.
What is Server-Side Email Signature?
A server-side email signature is one that is applied by the organization's mail server (Microsoft 365's Exchange Online, Google Workspace's Gmail SMTP gateway, or an on-premises Exchange server) rather than by the user's mail client. The advantage is universal coverage: the signature appears on every outgoing email regardless of whether the user composed it from a desktop Outlook client, mobile app, web browser, third-party email client, or a programmatic SMTP send. The disadvantage is that the signature is not visible to the user during compose, and it does not appear in the user's Sent Items folder (unless additional capture is configured). Server-side signatures are typically deployed through Exchange Online Transport Rules on Microsoft 365 or routing rules on Google Workspace. Server-side is the right choice when the priority is compliance enforcement (every email must carry the legal disclaimer) or when users send from many different clients. Client-side signatures are the right choice when WYSIWYG visibility and dynamic per-message personalization matter more.
Also known as
How does SyncSignature implement Server-Side Email Signature?
SyncSignature deploys signatures via the Outlook add-in for Microsoft 365 and the Gmail API for Google Workspace, both of which operate client-side. The signature appears during compose and in the sender's Sent Items folder.