I could see there being a hole in the system regarding e-mail for notifications. Maybe this could be solved with a notification system in the wallet. The only e-mail service I could see that would be able to handle this platform security-wise would be Lelantos (
http://lelantoss7bcnwbv.onion).
That's a valid concern

We have a couple of solutions to negate the risks of having email addresses stored in the ledger including encrypted in wallet messaging.
We'll be posting plenty of dev vids over the coming weeks as we build OneMarket so you guys can keep track of progress.