Most cell phone carriers make it easy to send e-mails directly to a cell phone via text message. You just need to have the correct e-mail address. This can be convenient if a friend or family member needs to get in contact with you quickly, and discreetly, but doesn't have his phone with them to send a text message. Also, the email address is fairly easy to figure out even if you don't know what it is.
Find out the cell phone carrier of the person you wish to send your e-mail to. This will be useful in determining her e-mail address. For instance, if her carrier is Alltell, the second half of the email address will be message.alltel.com. For Sprint, it will be messaging.sprintpcs.com. For AT&T, it will be @txt.att.net, for Nextel, @messaging.nextel.com, and for TMobile, @tmomail.net.
Find out the phone number of the person to whom you wish to send your message. This will determine the beginning part of the email. For instance a person's whose phone number is 415-522-5222 and whose carrier is Alltell, would be firstname.lastname@example.org.
Send your message by opening your e-mail client. Enter the email address as detailed above in the "To" column. Create a "Subject," write your message and click "Send."