Private messages
Some conversations aren't for the whole board. Private messages are member-to-member conversations, with the same comfortable editor topics use.
Starting a conversation
From a member's profile or the messages area, start a conversation: recipient, subject, message. Conversations thread like topics, so a running exchange stays one tidy thread instead of an inbox of fragments, and conversations can include more than two people when a small group needs a private space.
Knowing when you have mail
New messages light up your notifications, and depending on your settings, can reach you by email or push notification too. You'll know.
Private means private between participants; it doesn't suspend the board's rules. Harassment in PMs is still harassment, and the report option exists there for a reason.
The unwritten etiquette: public questions get public answers. Asking in the forum instead of PMing a helpful member means the next person with your question finds the answer too, and the helper only has to write it once.