Table of contents:

Introduction

CTP (Clear-Text Password) is a authentication scheme that can be used by very early versions (1.0.0452 to 1.0.0893) of the Offical Client.
This scheme is only available in MSNP2.

CTP offers very little security, with the password being sent unobfuscated and unencrypted to the Notification Server (NS), so it's understandable why it was ditched so quickly.

Procedure

C: USR TrID CTP I {user-handle} {password}
S: USR TrID OK (...)

Where {user-handle} is the handle (email address) the client is authenticating with.

Where {password} is the user's account password.