Steve Poe wrote: > > 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] <mailto:[EMAIL PROTECTED]>. the abc.com > <http://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 <http://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] > <mailto:[EMAIL PROTECTED]>.
It can be *done*. TMDA is one project that can do it, but I strongly recommend that you not pursue this. There are two major problems which can not be solved, both with the same root cause: spammers will use fake return addresses. That might not be a big deal if you're not getting much spam to begin with, but if you get a lot of spam, and try to reply to many spam with a challenge, your mail queue will fill up with undeliverable mail. Queue processing times may rise as your queue becomes larger, which is a major problem. Additionally, all of those undeliverable messages are going to end up in your postmaster account, and that will become unmanageable. (If you can't read your postmaster mail on a regular basis, you're doing it wrong) The second problem isn't technical, but social. Some of the addresses that spammers use are legitimate addresses that belong to other people. I expect that everyone here has been Joe Jobbed: some spam or virus engine used their address to send out a wave of email with your email address and you end up with hundreds or thousands of email from hundreds or thousands of different mail servers telling you that the mail that "you" sent isn't deliverable. Challenge schemes exacerbate this problem, because in addition to getting DSNs from some servers when my email address is used by a spammer, I'll get challenges, too! TMDA is written to avoid loops, and to allow you to receive messages from senders who won't ever respond to your challenges (bills, etc). Those are problems that have solutions. However, even with those problems solved, TMDA and similar schemes are going to cause problems for you, and for other people unrelated to your service. Please don't do it. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ courier-users mailing list [email protected] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-users
