Is there a way to find out if an email address is real?

Factual Questions
1

(I know, it’s computer help, I’m sorry, feel free to lock it…)
Is there any way–short of emailing the address and waiting for mail to bounce back–to find out for certain if an email address is registered or not?

2

Yes. First, find the mail exchanger for the e-mail address’s domain. For example, if the e-mail address in question is fred@example.com:


$ **nslookup**
>**set type=mx**
>**example.com**
Server:         10.0.0.2
Address:        10.0.0.2#53

Non-authoritative answer:
example.com     mail exchanger = 10 foo.example.org.

Authoritative answers can be found from:
foo.example.org        internet address = 83.128.149.52
>**exit**

(The stuff that you type is in bold text.) Then you need to telnet to the mail exchanger and attempt to send an e-mail to the e-mail address in question. (You won’t actually send an e-mail; you’ll actually abort the process before the mail is sent.)


$ **telnet foo.example.org**
Trying 83.128.149.52...
Connected to foo.example.org.
Escape character is '^]'.
220 foo.example.org ESMTP
**HELO testing**
250 foo.example.org
**MAIL FROM:<testing@example.com>**
250 ok
**RCPT TO:<fred@example.com>**
250 ok
**QUIT**
221 foo.example.org
Connection closed by foreign host.

If the e-mail address is legitimate, then you will get a “250” response from the server. Otherwise you will get a “550” response.

3

I think that is the holy grail of spammers. They would absolutely love something like that. I am pretty sure it doesn’t exist. There is no comprehensive directory of e-mail addresses or any other way that I can think of.

It is easy to just create new e-mail addresses. I have my own domain like lots of people do and I can create e-mail addresses at will and there is no good way for other people to know other than the blind attacks that many spammers engage in or perhaps information sharing by the domain owner.

4

That’s a pretty good suggestion psychonaut, but it doesn’t actually confirm that there is a valid mailbox of the specified name at the receiving domain; it only confirms that the mail server is prepared, at this time, to accept the message - it might return/reject it later if there is no matching mailbox, or it might already know there isn’t one and be accepting it for dropping into the postmaster account, or perhaps straight to a null account.

5

Might I inquire what the OP plans to do with this info if it becomes available? The old “send it and see if anyone answers or it gets returned” seems to work pretty well for most purposes.

6

True. However, you can usually tell if a certain mail server is indiscriminately accepting mail to any address by trying some RCPT TOs for obviously bogus addresses. If you get 250 responses for these, then you shouldn’t trust the 250 response you got from the address you were trying to check. On the other hand, if you get 550 responses from them, then you can probably trust the response you got from the address you were trying to check.

7

The OP has a name. It’s up above my post.

It’s not really up to me to discuss the details at the moment, but suffice it to say I may have sent the wrong email to the wrong address–a thoughtless mistake–and I’m hoping I can set it right.

8

Thanks for your help :slight_smile: I’m going to try that now…

9

Ooh, you’re good.