DCCM mail_host grabs smart_host setting?

Sven sven@dmv.com
Thu May 1 15:13:34 UTC 2003

From: "Vernon Schryver" <vjs@rhyolite.com>

>> From: "Sven" <sven@dmv.com>

>> ...
>> mail from someuser@somedomain.com coming from smtp.somedomain.com for
>> example should have mail_host of somedomain.com. If the mail doesn't get
>> rejected, it then proceeds on to the smart_host -->
>> INSTEAD I see the following in the messages in the log directory
>> mail from someuser@somedomain.com coming from smtp.somedomain.com ends up
>> with mail_host of smarthost.mydomain.com
>> I don't know if this is due to the way sendmail and dccm interact i.e.
> sendmail perform the smart_host substitution prior to dccm invocation?
>> ...

> I think sendmail passes the SMTP envelope Mail_From value to a milter
> filter such as dccm unchanged and unchecked.  Judging from a test or
> two just now, that seems to be true.
> Dccm then does a simplistic fiddling on the Mail_From value to pick out
> a value to call the mail_host.
> In other words, the only ways I think of for you to see those values
> involve the envelope Mail_From value cnotaining
> someuser@smarthost.mydomain.com
> That might happen if the original sender has configure an MUA to
> use that source address.  It might also happen if this instance of
> dccm+sendmail are not first, but the message has already been passed
> through an MX secondary or other MTA that replaced somedomain.com
> with smarthost.mydomain.com.

Based on the log messages, the env_from contains somedomain.com and the
mail_host contains smarthost.mydomain.com. The dccm machine, which is the
primary MX for the mydomain.com domain (with no secondary MX) receives the
mail directly from the outside world's mail servers; i.e. this is the only
instance of dccm+sendmail running and the only hop is the next one to the
smart_host. Keep in mind also, that EVERY message that is logged has a
mail_host value of smarthost.mydomain.com and env_from values that differ
based on what was sent via the smtp connection's env from: command. A sample
logfile entry:

3-IP: mail.computron.net ::ffff:
4-HELO: mail.computron.net
5:env_From: <xxxxxxx@hotmail.com>  mail_host=smarthost.mydomain.com

Now I have a similar setup on other machines that use mailertables instead
of smarthosts (due to the next hop varying based on domain name) and these
*do* have mail_host entries that correspond to the env_from entries, so the
issue seems to revolve around sendmail's handling of the smart_host


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