If you want to be able to send e-mails by clicking on an e-mail address while within a web browser, then you need to tell your browser what e-mail client you use.
In your case, you probably check your e-mail via a web based e-mail client. If you wish to be able to click on e-mail addresses, you'll need to download a piece of software which can manage your e-mail.
The easiest way to do this is to use Windows Live Mail. It's the newest version of Microsoft's free e-mail management client. To download it, go here: Windows Live Mail
Once you download and install Windows Live Mail, you need to set it up so that it can connect with your e-mail service. This is done quite simply by inputting the specifics of AT&T's e-mail server information and your personal account information. Server Information:
Check Box: Outgoing server requires authentication
Username: Full e-mail address
Passsword: Your Password
Here's a quick guide in case you want/need help: http://www.ehow.com/how_5863441_setu...dows-mail.html
If that doesn't work properly, you may need to contact AT&T Customer Support, as their server information could have changed.
With Windows Live Mail configured to use your AT&T E-mail Service, you simply need to tell your web browser that Windows Live Mail is your default e-mail handler now. Sometimes this is done automatically, if not, you can do so very easily through the settings/preferences menu on most web browsers.