Greetings All:

Now, when you bring up the page to send someone a new message, you should notice a link that says: "[verify user is accepting PMs] "

Just make sure you have a username specified under "Recipient:" first, then click the link.

This will let you make sure that the user allows PMs to be sent to them, that their PM inbox isn't full, and any number of other things that would stop your message from going through, BEFORE you waste all sorts of time typing up the letter.