Add-on vBulletin style form mail

On our vBulletin site we had the ability for any user to send an email to any other user who had agreed to allow that.

The form mail service did not allow the send to see the recipient's email address but the software sent it to them. The sender's email address is in the reply field when the message is received and if the receiver wants to continue the dialogue, they can reply.

This is a secure email introduction service and is the same technique when someone inquires about someone I know and asks to contact them. I do not give out my friend's email, but forward the request from the third part to my friend.

This does not appear to exist in XenForo and many of our users were surprised it was not there. I must confess I'm surprised that it is not here either.