my registered users can send each other proper emails (not private messages) through contact forms on their user profiles. When user A sends such an email to user B, I need user B to be able to reply to the email that was sent by A such that the two can start having an email conversation.
*) How can I encrypt the sender's and the recipient's email address such that the original email addresses of A and B are never revealed, even if the whole email conversation - after being initiated through the contact form - continues in their external email mailboxes?
Let me elaborate this a little bit further, even though I don't know if the path I am suggesting to take is at all feasible: To each user I assign a randomly generated key, e.g. 1k1 for user A and ki8 for user B. I would then set up the contact form on the profile of A such that every submission gets sent to firstname.lastname@example.org. Then, how can I make sure that every email going to email@example.com automatically gets forwarded to the actual email address of user A? If this could be done, I would simply replace the sender of this forwarded email with firstname.lastname@example.org and upon reply start over again.