Live E-mail VerficationTwo very cool tutorials that actually connect to the supposed mail server of whatever address the user specifies to see if the e-mail address actually exists.
http://www.devshed.com/c/a/PHP/Email-Address-Verification-with-PHP/
http://www.zend.com/zend/spotlight/ev12apr.php?article=ev12apr&kind=sl&id=1782&open=1&anc=0&view=1#notes........