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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

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Re^5: Determine if domain is actually used for email
by Your Mother (Chancellor) 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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[atcroft]: james28909: That particular questions was a bit of trick, actually (depending on the country you are in). More interesting is, if you are trying to subtract from an epoch time, for instance, you might have to consider when/if DST occurs for a location,
[atcroft]: because you may have to adjust the number of seconds you change from an epoch from 86400 (not to mention leap seconds)....
[atcroft]: james28909: Although if your program is using a database, you might be able to "pass the buck" to the database and ask it to do the date change for you....
[stevieb]: ++ atcroft

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