Direct messages
Besides the support inbox, Pigeon supports private direct threads between two or more logged-in Craft users — member-to-member messaging, author-to-editor notes, and the like.
Starting a direct thread
Post to the pigeon/threads/start action with type=direct and a list of recipients (usernames, emails or user IDs, space/comma separated):
Reading & replying
Each user sees their conversations through the craft.pigeon Twig variable and the built-in routes (/pigeon/threads and /pigeon/threads/<id>). Replies post to pigeon/messages/reply. Unread counts are tracked per user, so each participant has their own badge. See Front-end & Twig for the full API.
Notifications
When one user posts, the other participants are emailed a link to the thread and their on-site unread count ticks up — exactly the same fan-out used by the support inbox. See Notifications.