Disabling IP logging in the entire forum for all users (action logging remains, only the IP field will be empty)
Disabling IP logging by user in privacy settings
Deleting conversation messages some time after sending
Conversation by key (encrypted messages)
With services like Facebook now offering the feature to display your public PGP key on your profile, and to have all emails sent to you by Facebook encrypted with this key (source), and with Xenforo being a forum built on security, and especially with the recent addition of two factor...