

yggmail specifically, probably not. yggdrasil uses TCP/IP and the Meshtastic latencies to perform connections would be too high AFAIK. It would probably only work in a fairly well-connected network. yggdrasil could be used directly over a WiFi protocol but it would need fairly good reception to function.
N.B. I haven’texperimented with this myself.

Your work computer likely contains personally identifiable information. Microsoft very likely has a significant profile on what you do at work and could conceivably link that to your other identities outside of work.
Are they actually doing that? It’s hard to say. Microsoft does have relationships with data brokers like Snowflake Inc. and SCUBA plus its own internal capabilities like Xandr Inc.
Cross pollination is more than possible when employees use personsal devices to login to work accounts. Most of the people that I work with login to Slack on their personal device using Microsoft Entra SSO.