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.

yggmail is a fairly obscure and experimental take on email on a mesh network: https://github.com/neilalexander/yggmail

Graphene shills have been banging on this point for donkey’s ages. Reality is that many people use phones that are out of OEM support and many OEM ROMs are bundled with questionable software (Oppo, Samsung etc.) There are some decent criticisms to be made about LineageOS, but others to be made about Grapheme, like its Google-suggestive configurations, which is quite bad for security and privacy. Graphene says this is all optional and not part of the OS, but doesn’t include any equivalent F-Droid installer.