When I say run as instructed, I mean
1) The example email used in this thread was not as a result of an
open-relay on my Sendmail server
2) That when an email is addressed to a non-user of our domain, the
email server is currently configured to send a reply back to the sender
indicating that the addressee does not exist. Frankly, (as Craig points
out), most of these reply-to addresses are bogus. So it would be nice to
turn off this feature, but to continue to use
FEATURE(`accept_unresolvable_domains')dnl.
Thanks,
--Bill
On Thu, 2004-08-12 at 15:08, Bill Wesson wrote:
> 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
----
> Looking at sendmail.mc shows the listing:
> FEATURE(`accept_unresolvable_domains')dnl
>
> So apparently my Sendmail server is accepting mail from unresolvable
domains
> the opposite of what Craig stated below.
>
> The important point is that what I thought was a hack or open-relay was
> Sendmail running as instructed.
>
> Also, it appears that if I turn this feature off, email from our users
> off-site would be rejected. If I could turn it off, it would surely knock
> down the spam.
----
Of course you are assuming that the sendmail.cf you are using (the
actual configuration file), was created from the sendmail.mc file that
you are looking at. Unless you have run the m4 macro program against the
sendmail.mc file yourself that may not be the case...I haven't made a
study of what Red Hat does with each version and I definitely can't
vouch for other distro's. In cases where I am using sendmail for
sending/receiving mail, I actively customize sendmail.mc and run it
through m4 to generate a new sendmail.cf so I know what I have got.
This has become less material in spam control since most spam is
'forged' and relayed through seemingly legitimate sources.
What you are terming as the important point - whether you are running an
open relay can be tested by one of those provided sites which will or
won't allay your fears.
Craig
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