RE: Open Relay issue

top posted reply moved to bottom for readability

On Thu, 2004-08-12 at 08:01, Bill Wesson wrote:
> This is what I get 5 days earlier. (There are many more attempts.)
> Since the message was sent to a non-existent user at one of our domains, I
> think what I'm seeing here is Sendmail sending a message back to original
> sender that the email address is invalid. Would anyone agree with this
> assessment?
>
> Has anyone tried any of the open-relay assessment tools listed on Jeremy's
> link? Any recommendations of which one to try first?
>
> Thanks,
> --Bill
>
> Aug 4 17:25:03 payson sendmail[3689]: i750P31j003689:
> from=<Bain@123-stock.info>, size=1225, class=0, nrcpts=1,
> msgid=<LGGDNTNZOGUMMSUILVIH@123-stock.info>, proto=SMTP, daemon=MTA,
> relay=[65.182.130.29]
> Aug 4 17:25:47 payson sendmail[3699]: i750P6Aa003699: ruleset=check_mail,
> arg1=<Bain@123-stock.info>, relay=root@localhost, reject=451 4.1.8 Domain of
> sender address Bain@123-stock.info does not resolve
> Aug 4 17:25:47 payson sendmail[3698]: i750P31j003689:
> to=<carol@westerneng.com>, delay=00:00:44, xdelay=00:00:41,
> mailer=virthostmail, pri=121225, relay=westerneng.com, dsn=4.0.0,
> stat=Deferred: 451 4.1.8 Domain of sender address Bain@123-stock.info does
> not resolve
> Aug 4 17:25:47 payson sendmail[3699]: i750P6Aa003699:
> from=<Bain@123-stock.info>, size=1551, class=0, nrcpts=0, proto=ESMTP,
> relay=root@localhost
> Aug 4 18:04:47 payson sendmail[4132]: i750P31j003689:
> to=<carol@westerneng.com>, delay=00:39:44, xdelay=00:00:40,
> mailer=virthostmail, pri=211225, relay=westerneng.com, dsn=4.0.0,
> stat=Deferred: 451 4.1.8 Domain of sender address Bain@123-stock.info does
> not resolve
----
seems as though, this would be good administration... if
/etc/mail/sendmail.mc has a line like,
dnl FEATURE(`accept_unresolvable_domains')dnl

sendmail will not accept mail from unresolvable mail server. Seems
reasonable enough to me. If that troubles you, remove the dnl at the
start of the line and regenerate your sendmail.cf to allow it to accept
mail from unresolvable domains.

As far as testing for open relay, go for it.

Craig

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