Good question. You’ve got some options for what appears on the other person's Caller ID. If you don’t use Yahoo! Phone In, the number +1 (777) 777-7777 or "A Yahoo-owned number" is shown by default. Either way, your identity isn't revealed.

If you do have a Yahoo! Phone In number, the default setting will be that number Instead. If you have more than one, it will be the last number purchased.

You can customize this Caller ID information:

1. From Messenger’s main menu, select Preferences.
2. Select "Voice & Calls."
3. Under Phone In, change the “Use this number for caller ID” setting to whatever you want Caller ID to show.