Does your signature carry a web address and what service are the replies coming from?
It could be this:
Link Preview in Outlook.com
https://support.office.com/en-GB/art...c-a5362e881163
I’ve had a few replies from Outlook.com recipients where my original message carried a web link and Outlook.com inserted a preview in the reply. Unfortunately it is in the control of the Outlook.com user, not you.