How to Verify a Hotmail Email Addressby Chad Anderson
Typically, users can log in to a remote SMTP server used for sending email and request an account's validity by using the VRFY command. On Microsoft's Hotmail service, this command is disabled and the only response received will be "cannot verify." However, there is a work around since Hotmail lets you attempt to send emails without authenticating as a user. By attempting to set the recipient parameter you can see whether or not the mail box associated with the account exists.
Press the Windows and "R" keys simultaneously to launch the Run dialog. Type "cmd" into the text-entry field then press the "Enter" key.
Type "telnet" to launch the Telnet application. Type "open mx1.hotmail.com 25" to connect. Once established, type "HELO" to greet the server and begin.
Type "MAIL From:firstname.lastname@example.org" then type "RCPT To:email@example.com" where "address" is the Hotmail email you wish to verify. If you get an "Error 500" then the mail box does not exist for that account name.
Type "quit" to close your connection and "quit" again to exit Telnet, then "exit" to close the command prompt window.
- link IETF: RFC 2821