From Chillpoint Wiki

You may send private messages to other people in the community both in the server and on the website.

Server

There are two ways to send private messages on the server.

• /pm <id> <text> is the built-in SA:MP private message command. This command only supports IDs and also doesn't show the message you sent on your own screen. There is a minor bug in this command that will crash your game if you send a blank PM to someone.

• /m <id|nick> <text> is the scripted private message command. This command supports partial nicks much like the other scripted commands. This also shows both the messages you send and receive, making it easier to keep track of your conversation.

Chillpoint's website

Once you are logged in as a user you may use the private message pannel to send that user a message if they have an account.

IRC

In the IRC you may send private messages or an SMS to those in the server by sending a query/private message to Punky with #<nick> <text>. These messages can only be sent to those currently on their cellphone.
IRC also has it's own private messaging tool called a query. These can be sent by most IRC clients by double clicking on a user's name.