Direct notices
From StatusNet
Direct notices are dents send by you to another user, that do not appear in the public timelines. Sending a direct notice requires that both persons are subscribed to each other and you are on the same server (meaning direct notices are not federated).
To send a direct notice, go to your profile page and follow the Outbox link. As usual there is the big entry field to type your notice in but additionally there is a drop down list of all the people you can send a direct notice to. Select the recipient and type your message, then hit the send button. That's all you need to do to send a direct notice from the web interface.
Direct notices are limited to 140 characters, although the counter is not displayed in the web interface.
[edit] XMPP bot interface
If you like, you can also send direct notices through the XMPP Bot. Simple start your message there with
d recipient_name message_text
where recipient_name is the username of the recipient, and message_text is the text of the message you want to send to that recipient.
The bot will confirm that the direct notice was send.
[edit] Email notification
If you receive a direct notice StatusNet sends you an email informing you, about who send it to you and what's the content of the notice. You'll find it Inbox of your profile page.