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Sergio D. Caplan
*nix forums beginner
Joined: 01 Jun 2006
Posts: 1
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 Posted: Thu Jun 01, 2006 2:38 pm Post subject:
VRFY
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Hello All,
I have a question about qmail, and am not a programmer in the Unix/Linux
arena, but I do know enough to not just cause damage, but waste people's
time by not asking questiosn the right way. Let's hope this isn't one of
those times.
I am under the impression that some email gateways (to catch spam) will
verify not just the sending email domain, but also that the sending email
address is valid.
Can I assume that if my email server has qmail, it is qmail that responds to
these verification requests?
Many thanks,
Sergio |
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Markus Stumpf
*nix forums Guru Wannabe
Joined: 11 Jan 2005
Posts: 122
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| Posted: Thu Jun 01, 2006 3:00 pm Post subject:
Re: VRFY
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On Thu, Jun 01, 2006 at 10:38:13AM -0400, Sergio D. Caplan wrote:
| Quote: | I am under the impression that some email gateways (to catch spam) will
verify not just the sending email domain, but also that the sending email
address is valid.
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Yes, but they will not use VRFY, but RCPT TO.
| Quote: | Can I assume that if my email server has qmail, it is qmail that responds to
these verification requests?
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Yes. It even answers to VRFY requests:
VRFY joe@example.com
252 send some mail, i'll try my best
Implementing VRFY these days would be a wonderland for spammers to
clear/create lists (from dictionaries) fast and easy.
\Maex
--
SpaceNet AG | Joseph-Dollinger-Bogen 14 | Fon: +49 (89) 32356-0
Research & Development | D-80807 Muenchen | Fax: +49 (89) 32356-299
Don't claim that you know everything. Besides not being
true it is very irritating to those of us who do. |
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Charles Cazabon
*nix forums Guru
Joined: 08 Jan 2005
Posts: 805
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| Posted: Thu Jun 01, 2006 3:20 pm Post subject:
Re: VRFY
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Sergio D. Caplan <Sergio@WarpTV.com> wrote:
| Quote: |
I have a question about qmail, and am not a programmer in the Unix/Linux
arena, but I do know enough to not just cause damage, but waste people's
time by not asking questiosn the right way. Let's hope this isn't one of
those times.
|
:)
| Quote: | I am under the impression that some email gateways (to catch spam) will
verify not just the sending email domain, but also that the sending email
address is valid.
|
Well, there are some MTAs and such that claim to do this. What they do is an
"SMTP callback"; when they receive a connection from a client and receive the
envelope, they connect back and try to reverse the client's request. If the
RCPT TO: command is accepted, they then quit that connection and accept the
(waiting) client's message.
Needless to say, this is a really, really bad idea. Picture two such servers
with the same feature turned on...
| Quote: | Can I assume that if my email server has qmail, it is qmail that responds to
these verification requests?
|
Yes.
Charles
--
--------------------------------------------------------------------------
Charles Cazabon <qmail@discworld.dyndns.org>
Read http://pyropus.ca/personal/writings/12-steps-to-qmail-list-bliss.html
My services include qmail consulting. See http://pyropus.ca/ for details.
-------------------------------------------------------------------------- |
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Brian T Glenn
*nix forums beginner
Joined: 17 Mar 2005
Posts: 22
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| Posted: Mon Jun 12, 2006 9:01 pm Post subject:
Re: VRFY
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On Thu, Jun 01, 2006 at 09:20:33AM -0600, Charles Cazabon may have written:
| Quote: | Sergio D. Caplan <Sergio@WarpTV.com> wrote:
I am under the impression that some email gateways (to catch spam) will
verify not just the sending email domain, but also that the sending email
address is valid.
Well, there are some MTAs and such that claim to do this. What they do is an
"SMTP callback"; when they receive a connection from a client and receive the
envelope, they connect back and try to reverse the client's request. If the
RCPT TO: command is accepted, they then quit that connection and accept the
(waiting) client's message.
Needless to say, this is a really, really bad idea. Picture two such servers
with the same feature turned on...
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I believe that the callback is done using MAIL FROM: <> in the manner of
a bounce message. This stops loops the same way it stops them in bounce
messages.
--
http://www.delink.net/
The man who sets out to carry a cat by its tail learns something that
will always be useful and which never will grow dim or doubtful.
-- Mark Twain |
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