how to find out if an e-mail address exists?

stuey · 10-05-2005 12:56AM #1

i need to send a few e-mails to people i know that there e-mail address is of the form forename.surname.X@domain.com where x is a number. is there anyway that i can "ping" for want of a better word, an e-mail address to see if it exists?

smorton · 10-05-2005 01:04AM

stuey wrote:

i need to send a few e-mails to people i know that there e-mail address is of the form forename.surname.X@domain.com where x is a number. is there anyway that i can "ping" for want of a better word, an e-mail address to see if it exists?

the following code:
To:forename.surname.X@domain.com
from:me@mysite.com
subject:yoohoo. anybody there?

not that i know of but if you send them an email and it doesn't exist you'll get an automatic email shortly afterwards saying that delivery failed. any good to you?

muckwarrior · 10-05-2005 01:26AM

Yeah it's possible. You can do a reverse DNS MX record lookup. Can't remember exactly how offhand. Prob easier to just do it the way mentioed above.

cgarvey · 10-05-2005 09:01AM

smorton's way is the only definitive way to test. If you don't want to be detected you can query the mail server directly, but a lot of mail servers are configured to accept mail point blank, and then deal with whether or not the user exists (after accepting the mail). The following test won't work in those cases, but if the mail server does a realtime user lookup, it will....

nslookup -type=mx thedomain.com

will give you something like

thedomain.com  MX preference = 10, mail exchanger = mail.thedomain.com

and you need the mail.thedomain.com bit.

telnet mail.thedomain.com 25

and you should get some sort of a response which will probably mention "220" and "SMTP", then type

helo myowndomain
mail from: mytestmail@mail.com
rcpt to: theaddressiwanttotest@thedomain.com

If you get "OK" after that then either the user exists, or the server is configured to accept all mail, and process it after the SMTP session. Type "quit" (and return) to get out of the session.

.cg

Khannie · 10-05-2005 09:14AM

cgarvey->setNetworkingGeekStatus(cgarvey->getNetworkingGeekStatus() + 1);

One suggestion on top of cgarveys: Turn on local echo in your favourite telnet client. Otherwise you'll be looking at a blank screen when typing your protocol bits.

muckwarrior · 10-05-2005 11:38AM

cgarvey wrote:
mail from: mytestmail@mail.com
rcpt to: theaddressiwanttotest@thedomain.com
If you get "OK" after that then either the user exists, or the server is configured to accept all mail, and process it after the SMTP session. Type "quit" (and return) to get out of the session.

.cg

AFAIK most servers will only validate the domain in the RCPT TO command before returning an OK. It won't check if the actual user exists.

To check if a particular user exists on the server youshould use the VRFY (verify) command. e.g vrfy user@domain.com. Technically you could use a wildcard to return all users but most servers won't allow this.

Lump · 10-05-2005 12:33PM

smorton wrote:

the following code:
To:forename.surname.X@domain.com
from:me@mysite.com
subject:yoohoo. anybody there?

not that i know of but if you send them an email and it doesn't exist you'll get an automatic email shortly afterwards saying that delivery failed. any good to you?

That's what I'd do...

John

Capt'n Midnight · 10-05-2005 05:57PM

you can use MX records to verify that the bit after the @ symbol is valid

as for the bit in front of the @ symbol - that is entirely down to the email server to validate, and if it's configured to block replies or not, some are.

If you had an email server that dialed up you could have a situation where your email was delivered to the ISP's mail server (do you get a delivery reciept from it ??) and not picked up by the real server till later. That server may not send a non-delivery back for several days if at all.

There used to be stuff like FINGER - but privacy concerns and the insiduous nature of SPAM mean they no longer work and that most organisations don't hand out mailing lists willy nilly.

how to find out if an e-mail address exists?

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