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Re^4: Determine if domain is actually used for email

by Limbic~Region (Chancellor)
on Oct 04, 2011 at 19:17 UTC ( #929646=note: print w/ replies, xml ) Need Help??


in reply to Re^3: Determine if domain is actually used for email
in thread Determine if domain is actually used for email

Your Mother,
I have no idea where UDP came into the conversation since SMTP is a TCP protocol. I agree that there is no way to be sure unless you can deliver mail to a recipient and get a DSN or, preferred, a response. Seeing if the server is listening on port 25 and is responding in a manner consistent with a SMTP server and not giving a 521 status code is a pretty safe bet though.

Cheers - L~R


Comment on Re^4: Determine if domain is actually used for email
Re^5: Determine if domain is actually used for email
by Your Mother (Canon) on Oct 04, 2011 at 19:35 UTC

    Good to know. Thanks. "Safe bet" still sounds like gambling. :P

      Seeing if the server is listening on port 25 and is responding in a manner consistent with a SMTP server and not giving a 521 status code is a pretty safe bet though.

      So am I right that, although not 100% reliable, this might be a good way to check if a domain has an actual email with no risk to be caught as spammer? Is there a code which implements this approach?

        Depends how many servers you are looking at and how good the IDS is on the site. If it was enough of a problem, I could see using that fingerprint to tag a site to watch behavior more closely. ISTR discussions about this many years ago on SPAM-L. Perhaps browsing the archives for doorknocking, testing addresses, and some similar search terms might be useful.

        --MidLifeXis

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