You could use the winsock control, connect to port 25 of "provider.com" and send a "VRFY r.vzit" command.

>Hello,
>
>Does anybody know a way to verify an email address. I mean just to see if the emailaddress exists. But without sending the user a real email. Example: r.vzit@provider.com
>First I like to know if the domain: "provider.com" exists.
>And then I like to know if the user "r.vzit" exists in the "provider.com" domain.
>
>Does anybody know a way to do this?
>
>Thanks,
>Ron van Zitteren