way to check an email without sending it??

Bill Moran wmoran at potentialtech.com
Mon Oct 5 17:59:26 UTC 2009

In response to Gary Kline <kline at thought.org>:
> 	Hey Guys,
> 	Is there a way I can tell that an email address, say
> 	joe at foo.com 
> 	is still valid without joe knowing that I am curious?  --And,
> 	yes, this isn't a FBSD-specific question... .
> 	thanks for any insights,

Sure.  Telnet to the service and start a SMTP transaction, but then abort it:

$ telnet mail.potentialtech.com 25
Connected to mail.potentialtech.com.
Escape character is '^]'.
220 mail.potentialtech.com ESMTP If you spam me I will bounce you
helo mail.potentialtech.com
250 mail.potentialtech.com
mail from: <wmoran at potentialtech.com>
250 2.1.0 Ok
rcpt to: <joe at potentialtech.com>
450 5.7.0 <joe at potentialtech.com>: Recipient address rejected: User unknown in local recipient table
221 2.0.0 Bye
Connection closed by foreign host.

If you don't get a rejection after the "rcpt to:" line, then you know the
server will accept the mail and you can close the connection without
completing the transaction.

Note, that this is no guarantee.  Some spam catching nonsense may accept
the mail right up to end, then throw it away without delivering it.

Bill Moran

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