Yes, it actually contacts the server to make sure the address is valid and usable.
http://drupal.org/project/email_verify

To use it with comments (patch): http://drupal.org/node/458758

A tip to use with any form: http://drupal.org/node/898726
 
Nancy
 
Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.


From: Shérab

> I'll mention one that probably no one else will: Email Verify.

Close enough to my own suggestion ! :-)
But I didn't knowit was possible to verify e-mail validity beyond purely
syntactic verification.

> It checks to see if they enter a validand reachableemail address. It
> has no visible component, so it may not even be on your radar, but I
> consider it indispensable in the war against spam.

It is for sure helpful !

Could you provide pointers ?