On Sun, 19 Aug 2001, Shane Lee wrote: > I'm looking at different ways that I would be able to check to > see if an email address exists, for purposes of my Mercury > email system for CircleMUD. > I ran across the idea of using ping, but kinda ran into > a tricky situation. While ping readily transmits packets to > www.yahoo.com and mail.yahoo.com, it won't recognize my > email address: tacodog21@yahoo.com. I can't ping an email address. Ping is only used to determine if a host is alive. Even that is not a sure-fire method, because many large companies block ICMP packets at their firewall to prevent D0S attacks. The only way to validate an email address is to actually send an email to the address. Some SMTP servers will immediately declare a user (or email address) as invalid during the SMTP conversation. Others will accept the email no matter who it is destined for and then return an error message to the sender. Since both methods are acceptable (and neither is dominant as far as I know) you can't rely on either method. Your best bet is to send an email to the address and make sure to include the following headers: Reply-To: you@foo.com Errors-To: you@foo.com From: you@foo.com ... in addition to the normal headers found in an email. Until you fully understand email and all of the related RFC standards for SMTP, I would not attempt to do this. Like you said, this would probably result in doing nothing more than opening up potential security holes and aggrivating various email sysadmins around the world. -- Zeavon Calatin, Magemaster of the Realms Spear of Insanity -- telnet://spear.kilnar.com:1066 http://spear.kilnar.com/ -- +---------------------------------------------------------------+ | FAQ: http://qsilver.queensu.ca/~fletchra/Circle/list-faq.html | | Archives: http://post.queensu.ca/listserv/wwwarch/circle.html | +---------------------------------------------------------------+
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