it works over regular smtp and imap, via your usual relays and email servers, etc. If you can send and receive email, then I guess it should work fine.
If you can send and receive email, then I guess you have been bitten at least once by its store-and-forward, best-effort nature. In other words, no guarantees on message delivery time (two days delayed? Working as designed!), message ordering, or even whether it's delivered at all. I literally know of no worse medium for chat than email, even considering raw ethernet frames and pigeon post.
"It is sort of available everywhere" is email's only selling point - that's not enough to justify "let's build everything on top of it".
