sendmail-8.12.6+cyrus-imapd-2.0.17: check presence of the cyrus mailbox during establishing SMTP connection

Gary Mills mills at cc.UManitoba.CA
Tue Nov 4 22:45:58 EST 2003

On Wed, Nov 05, 2003 at 01:57:01AM -0000, Mike Brodbelt wrote:
> FWIW, my interest in it isn't for authentication, but rather as spam
> control. At the moment, we get a lot of junk addressed to bogus users in
> our domain. This is accepted by sendmail, which then tries to deliver it
> to Cyrus. Delivery fails with a no such user error, and a bouce is
> generated, which invariably goes nowhere, as the spam had a forged from
> address. I'd like to be able to send 550 messages back in the initial SMTP
> session when the local user doesn't exist, but I don't want to switch
> sendmail into interactive mode for all deliveries.
> ATM, the only way to achieve this involves breaking Cyrus' "black box"
> model. I'm very interested in anything that can present a solution to

Sendmail has a mailer flag, usually associated with the `local' mailer,
but one that could be associated with the `cyrus' mailer.  When this
flag is present, sendmail will look up the recipient in a database of
users.  All you have to do is to point it at the same database of users
that is employed by Cyrus.  Then, if the user is not found, sendmail
will reject the mail during the SMTP dialogue.  In my case, I use NIS
for the user database, but there are many other ways to do it.

-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-

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