Enda,
Thanks for your response. Before I sent the original email, I did search on
challenge-response
and courier to get an idea of the pros/cons. We do filter out most unwanted
emails with spamassassin,
but we want to give automation to our mailserver and some additional control
to our the users. I understand we
could get caught a in loop for one challenge-response to another.
What open source tools that work in this area?
Steve
On Tue, Jul 15, 2008 at 1:24 PM, Enda <[EMAIL PROTECTED]> wrote:
> On Tue, Jul 15, 2008 at 8:16 PM, Steve Poe <[EMAIL PROTECTED]> wrote:
> > I am new to email servers, so pardon my ignorance.
> >
> > The small company I work for has an email server where they want
> > to create an approved/whitelist for emails coming from the outside. For
> > example,
> > I email [EMAIL PROTECTED] the abc.com mailserver does not see my email
> > address in approved list for the user account and/or as a company-wide
> > contact list, so the abc.com mail server sends a reply to me to confirm
> I
> > sent
> > the email that I *really* wanted to send the email to [EMAIL PROTECTED]
> > Meanwhile,
> > John receives my email, after confirmation of my response, then he adds
> me
> > to his personal contact/approved list. The mail administrator found out
> > that
> > I am
> > a new client of abc.com so I am added to the company-wide approved list.
> >
> > We are running Courier 0.53 on Centos Linux 4.4
> >
> >
> > Is this possible?
>
> It sure is possible and there are projects in the opensource world and
> products in the proprietary world which you can use to do exactly this.
>
> Consider this though? What if I use the exact same system and you email me?
> I'll issue you a challenge, your email system will respond to mine with a
> challenge, to which I'll respond to you with a challenge for infinity,
> without the mail getting delivered. Simply put, if everyone used this
> scheme, nobody would get any mail, and if you use it, you're immediately
> not
> going to get mail to or from some other organisation that does use it nor
> will they get email from you.
>
> Want to buy airline tickets? Airline emails you your eticket, your email
> system responds to them with a challenge "did you really send this to me",
> the automated airline ticketing system won't respond, you won't get your
> airline ticket. Even if you whitelist the airline, you can't be sure they
> wont be delivering the eticket through a content distribution partner which
> won't be in your whitelist.
>
> Ironic that you questioned this today, as one of my email customers is a
> subsiduary of a French multinational who run such a system. One of my guys
> went on holidays and put up a vacation notice. I only know he's on vacation
> because of the postmaster emails I've been getting saying that his vacation
> notice was undeliverable.
>
> I just consider such a system bad manners because you're shoving your spam
> cleaning burden onto me, do it yourself.
>
> Its bad bad form, don't go there, and talk your customer out of it.
> Blacklisting will reclaim all mailsystems from the spam burden, and add
> spamassin into the mix to pick up the slack and you're home and dry.
>
> HTH,
>
> -Enda.
>
>
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