Dnia 23.11.2019 o godz. 20:05:07 Tom Ivar Helbekkmo via mailop pisze:
> In the olden days, one would simply write a script, using expect(1) or
> similar, to go through the addresses, connect to the target MTAs, and do
> an SMTP VRFY on the recipient address.  Today, I suspect that most MTAs
> will refuse to service a VRFY request.

SMTP VRFY was basically never widely adopted. There were always many mail
servers that didn't accept VRFY.

That's why MTAs that have "sender verification" feature on incoming mail do
it by just trying to send mail back to the sender and checking the reply
they get on RCPT command. If RCPT is accepted, they assume the e-mail
address exists (and accept mail from that sender), if it is rejected, they
reject the incoming mail too, assuming the sender doesn't exist. After
that, they just send RSET, cancelling the send attempt.

As someone already noted, there are also standalone tools that implement the
same technique. However, I don't know what impact on reputation could have a
large-scale use of this address verification method.
-- 
Regards,
   Jaroslaw Rafa
   r...@rafa.eu.org
--
"In a million years, when kids go to school, they're gonna know: once there
was a Hushpuppy, and she lived with her daddy in the Bathtub."

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