Using a clearnet provider is fine as long as you keep scripts disabled, use GPG and use Tor, and take all of the other security precautions possible. Something better would be nice, but I just am not aware of anything really better right now. I think BitMessage has a lot of maturation to do before it should be used for anything sensitive, Freenet has an email like thing but it requires you to communicate with other people running Freenet. It really isn't that hard to make a simple hidden service for private messaging, you could do it with a cheap VPS if you are okay with that level of security, or certainly with a bottom of the line dedicated server. Maybe people should pool some Bitcoins and have somebody trusted like Astor set it up, doesn't really matter if they turn evil in the future because you always use GPG anyway right? I don't have time to setup an private messaging server right now or else I would do it on a VPS and pay for it for a year if somebody sent me $600 worth of Bitcoin A little harder to do something like Tor Mail (allowing actual E-mails to exit and come in, rather than internal private messaging) though, it would require two servers and some more intensive configuration. Why not just use the forum PM system? If you just need a secondary way to communicate with vendors in case of emergency, a secondary unrelated internal PM system would work and there isn't need for E-mail, or is there some need for E-mail like talking to Chinese vendors? Hm, I guess maybe need two servers if you want something like Tor Mail, and a bit harder to configure.