> this is only a half-solution, but it's fairly easy to find out whether a
> given /machine/ exists. perl has the built-in routine gethostbyname()
> which will do a standard DNS lookup for you.
> .
> .
> .
>
> assuming you get a legitimate network address, at least you know the
> machine exists.
As others have pointed out, this doesn't work if the "machine" part of the
e-mail address is an MX record. That is, it is possible to put "machine names"
in what is called an MX record in a domain name table. An MX record for one of
these "machine names" specifies the actual machine that the mail should be sent
to. Mailers (like sendmail) look up MX records then send the mail to the real
mail machine.
Typically this is used so that you can send mail to <user>@<domain name>
even though there is no actual machine by that name. You can send mail
to me to [EMAIL PROTECTED] Your mailer will actually send the mail to
sauron.mordor.org.
So if you want this to work, you will have to first look up the MX record to
see if it exists. If it doesn't then you can try the machine name.
> checking the address itself would be harder.. for that, you'd have to open
> a socket connection to the mailserver, and ask it to verify the address.
> that's certainly possible.. it's part of a standard SMTP transaction, in
> fact.. but it's not trivial.
To make life even more complicated, many sites disable the verification
fuction for security reasons.
Bob Weaver
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