Threads

Inbound and outbound mail in one conversation.

A reply that cites Message-ID, In-Reply-To, or References joins the existing thread. A new message with none of those starts a new one.

list_threads and read_thread return a thread only when it has Allowed inbound mail, or mail this agent sent. reply_to on send_mail is an Allowed item, an outbound id, or a Message-ID.

If you pass a locked message as reply_to, the send fails closed. The locked body is not returned.