If you want to send a short email and have it delivered to the recipient's cellphone as a text message (SMS), it can be done if you know the recipient's cellphone number and the mobile phone service provider. These details tell what the email address associated with the receiver's mobile phone is. The update messages delivered over wireless networks and alert messages such as bill alerts from the bank, work on the same principle. Every cellphone has an associated email address, which is used to receive or send email. Most carriers use “SMS gateways” which convert the email messages into text messages. These SMS gateways can be extremely useful when you are sending a text message or SMS to any international cell number. All you need to know is the ten digit cellphone number of the recipient and the domain name of the carrier. It is as easy as sending a normal SMS or email. If you want to know how you can make use of this incredible service and send free text messages through emails, here is some help:

Steps to find the email address of your cellphone:
The syntax @ helps you discover the email address linked with the cellphone. For example, for Virgin Mobile it is number@vmobl.com. If you are using ATT or Cingular service provider, to find the email address either send an SMS to number@txt.att.net or you could send an MMS to number@mms.att.net. To give an example, to SMS the mobile number 1234567890, the service provider of which is Virgin Mobile, send an email to 1234567890@vmobl.com. Simply by knowing the service provider’s domain address, you can easily send emails to any mobile number.
However, there is an alternative method to know the email address of the mobile phone:
Compose a text message from your cell phone and send it to your email address. The received email will also include your mobile phone’s email address. In case you are unable to find the carrier’s domain, then try using Teleflip service. Unfortunately, as of now this service is only accessible to some countries.
Here are some of the domains of popular service providers in the US to send free SMS from your computer:
Alltel: 10-digit mobile number@message.alltel.com
Boost Mobile: 10 digit mobile number@myboostmobile.com
AT&T or Cingular: 10 digit mobile number@cingularme.com or
10 digit mobile number@txt.att.net (SMS) or
10 digit mobile number@mms.att.net (MMS)
Sprint Nextel or Sprint PCS: 10 digit mobile number@messaging.sprintpcs.com or
10 digit mobile number@pm.sprint.com(MMS)
Nextel: 10digit mobile number@messaging.nextel.com
Virgin Mobile USA: 10 digit mobile number@vmobl.com
Mentioned below are a few popular mobile phone service providers in India with their domain addresses:
BPL – 10 digit mobile number@bplmobile.com
Airtel India: 10 digit mobile number@aircelmail.com
10 digit mobile number@airtelchennai.com (for Chennai recipients and Skycell users)
10 digit mobile number@airtelkol.com (for recipients in Kolkata)
10 digit mobile number@airtelkerala.com (for recipients in Kerala)
Idea – 10 digit mobile number@ideacellular.com
Aircel – 10 digit mobile number@airsms.com
Escotel – 10 digit mobile number@escotelmobile.com
Celforce – 10 digit mobile number@celforce.com
BSNL – 10 digit mobile number@bsnlumn.com (for recipients in North India)
10 digit mobile number@bsnlums.com (South India)
10 digit mobile number@bsnlume.com (East India)
10 digit mobile number@bsnlumw.com (West India)