On Thu, 3 Dec 1998, Jeffrey Goldberg wrote:
> What I need is a quick email address verifier.
>
> exim -bt ADDRESS
>
> helps determine whether the address is well formed and whether there is
> a hostname (or MX) for the address, but if the address would generate a
> 5?? directly from that host, I can't coax out of a one liner.
What do you propose as the algorithm? You look up the MX record and you
get back a list of 5 hosts. What do you do next? Try them in order till
you can connect to one? What if they are all inaccessible? Even if you
connect to one, it may be the "backup backup" host, which has no
knowledge of valid local parts, so just says OK. Or maybe it operates
like AOL's mailer, which accepts all local parts, and then sends back an
error message for those it doesn't understand rather than bouncing at
RCPT TO time. (The RFCs explicitly allow either behaviour.) So then you
try to mail to that address, and ultimately you get back "not known", so
the original OK answer isn't actually true. A similar thing could happen
even if you get to the real end host and it does validate at RCPT TO
time, if the user has a broken .forward file which goes to some bad
address (maybe via a chain of .forwarding).
If you implement anything like this for others to use, you will get
plenty of complaints, I think. The One True Way to check an email
address is to send it a message.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
--
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