You can send text messages to friends who have service with any of the following wireless carriers:
USA: AT&T, Cingular, Verizon Wireless, and T-Mobile
India: Hutchinson, Airtel, Spice, Escotel, and Reliance
Singapore: Singtel
Thailand: AIS and DTAC
Malaysia: TMTouch
Philippines: Smart and Globe
Here’s how:
Choose one of these three primary ways to start a text message:
Click the Actions menu in Yahoo! Messenger and select "Send an SMS Message."
Or, right-click the contact from the Messenger List and select "Send an SMS Message".
Or, click the text message icon in the address book.
OK, now enter your friend’s mobile phone number. Make sure you add the country code (for example, +91) for International numbers.
Type your message and click Send.
Note: To use the right-click menu or Address Book icon, you must have a mobile number listed in the Contact Details for that person.
Country codes:
USA +1
India +91
Singapore +65
Thailand +66
Malaysia +60
Philippines +63