With the Fully server-side setting enabled, the default/reply email signatures are added when the email is sent. They are visible at the recipient's end, not when you compose the email.
Enable this only if you're not using the 365 add-in > Learn more.
It ensures the email signature is applied to all emails across all clients upon sending.
The default email signature is added at the bottom of the email chain, and the reply/forward email signature is added to the email chain.
If a 'divider' is found in the email chain, the reply signature is added above the divider' (screenshot below).
The 'divider' is found in Outlook on Windows/Mac and in Outlook on the web (browser).
Requirements
Microsoft 365 environment is required.
How to configure server-side
Learn how to set up server-side in this KB guide.
How to enable 'Fully server-side'
Open the 'Preferences' menu (top right hand):
