You can send mail to any player even if he is not online. They will get the message next time they log in. To send mail use the compose "recipient" "message" command. The cost of one mail is 5 pt.
If someone has sent you a mail you will get a notification when you log in. Use mail command to read it.
To avoid detection through player list use invisible command. For the cost of 10 pt your nickname will disappear from the player list for one hour

Official Personal Artefact web site:
http://www.darkswords.net/pindex.php