Is that possible today?
Although I'm new at YAF, it appears to me that by default users cannot see other users' e-mail when looking at their profile.
If you don't want them sending e-mail (which doesn't reveal the e-mail address as it sends through the forum), uncheck "Allow Email Sending" under Host Settings and they will only be allowed to PM each other.
"It's a case of RTFM.. the only problem being we don't have a manual!"
When I post FP:Mek in a topic, I'm leaving my footprint there so I can track it once I get into coding/supporting. (Yes I stole this off Ederon 🙂 )