The "xtell" command sends a message to a user, just like "tell" does. However, "xtell" will not alter the setting for who-you-told-last. This setting affects how the "." alias will function. A "tell" sends a message and resets the who-you-told-last variable to a new user. The "xtell" command will leave this setting intact, meaning that you can still use the "." alias to "tell" to a person you are having a conversation with. The "xtell" command allows for a brief comment to someone while you are having a longer chat with someone else.
SPECIAL NOTE: Xtell works only with tells to players, not to channels.