Possibly AI-driven E-Signing, defined at the AI-supported document generation stage(?), shown as part of the Microsoft Syntex plugin to Copilot 365 demo at MS Build Day #2. Among other things, Syntex „will allow you to build new documents“ from existing content.

„When done, the plugin can add Syntex eSignatures for your approval“.

A quick websearch hints at extensibility wrt. to possible E-Sign providers: „You can send electronic signature requests using Syntex, Adobe Acrobat Sign, DocuSign, or any of our other eSignature partner solutions and your content stays in Microsoft 365 while it’s being reviewed and signed“. https://www.microsoft.com/en-us/microsoft-365/blog/2022/10/12/welcome-to-microsoft-syntexcontent-ai-integrated-in-the-flow-of-work/

This happened in the context of Word, so maybe this is less about Syntex and more about Copilot proposing signers, based on the E-Mail addresses in the document?