Rebol [ Library: [ level: 'intermediate platform: 'all type: 'tool domain: 'email tested-under: 1.3.1.3.1 support: none license: 'BSD see-also: {dig.r} ] title: "SMTP challenger" file: %email-check.r author: "Graham Chiu" rights: 'BSD date: 27-Nov-2005 needs: {dig.r from the rebol.org library} purpose: { Issues an smtp challenge to see if recipient email address exists. Some mail servers will respond okay anyway to protect users from spammers. } ] do %dig.r get-mx-ip: func [ "Returns the ip address of the lowest MX record" nameserver [tuple!] domain [string!] /local ans result ][ result: copy [] ans: read to-url rejoin [ "dig://" nameserver "/MX/" domain ] foreach rec ans/answers [ repend result [ rec/rdata/preference rec/rdata/exchange ] ] ; get the lowest preference for the MX record result: second sort/skip result 2 foreach rec ans/additionals [ if rec/name = result [ return rec/rdata/ip ] ] ; return read join dns:// result result ] emails: [ %carl--rebol--com %cyphre--rebol--com %holger--rebol--com %compkarori--gmail--com ] name-server: 203.96.152.4 { use your own DNS server for this! } foreach email emails [ prin [ "Email: " email " " ] set-net reduce [ "<>" get-mx-ip name-server form find/tail email "@" ] smtp-port: open [ scheme: 'smtp ] if error? try [ insert smtp-port {MAIL FROM: <>} insert smtp-port rejoin [ {RCPT TO: <} email {>} ] print "OK" ][ print "Error" ] attempt [ close smtp-port ] ]