Re: PING - email possibilities?

From: Zeavon Calatin (
Date: 08/19/01

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
> and, it won't recognize my
> email address:

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:


... 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://

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