More on Masquerading

[Alexander Dalloz]

Am So, den 15.08.2004 schrieb Ow Mun Heng um 12:19:

> What exactly does genericstable do? (Sorry, writing this mail off-line)

Please read my explanations in the posting I just wrote for Harry.

> My Problem.

> @work = mails must be sent out using the corp exhange server (smart host
> feature _must_ be implemented via sendmail.mc)
> 
> @home = mails are sent out w/o using smart host. Meaning, I have to
> actively re-compile sendmail.mc each time between office and home to
> send out emails. Cause @home, mails gets relayed directly to the
> receipient's MX. 

You use the same email address @wdc.com from work too at home? Can you
use the business mail server as smart host as well from at home (SMTP
AUTH)?

> > It is not an internet FQDN, just my own made up domain for my local
> > lan.  Therefore will never be resovable by dns lookups.
> Just as I thought. And what/how does this affect mail sending?

It will lead to rejects by foreign MTAs. For SPAM fighting most MTAs
meanwhile don't accept mail with 'faked' sender addresses.
 
> > My attempt at using generics tables consisted of adding:
> > (see sendmail2.mc below for the full settings)
> > 
> >   FEATURE(`genericstable')dnl
> >   FEATURE(`generics_entire_domain')dnl
> > 
> > And to /etc/mail/genericstable:
> >    reader               reader at newsguy.com
> What does this achieve?  I don't see a genericstable in my
>  /etc/mail/ directory

You have to create a genericstable your own, if you like to use that
one. For each domain in class {G} - the generics-domains listing is
missing here - the sender address on the left side in the genericstable
map file is rewritten to what is to be found on the right hand side.

> > Aug 14 19:31:34 reader sendmail[12324]: i7F0VTsA012322:
> > to=<reader at jtan.com>, ctladdr=<reader at reader.local.net0> (500/500),
> > delay=00:00:04, xdelay=00:00:04, mailer=relay, pri=120355,
> > relay=smtp.newsguy.com. [129.250.170.69], dsn=5.6.0, stat=Data format
> > error
> 
> What's data format error? And I see that your relay is =
> smtp.newsguy.com, which resolves to your Inet Public IP.

smtp.newsguy.com is Harry's ISP's smart host MTA.

> For my case, it gets relayed to the localhost (127.0.0.1)'s smtp. which
> then hands it over to sendmail to contact the MX.

Yes, this is part of communication between Harry's Sendmail and the
smart host.

> What I want to know is, is there a way to say that I want mails to be
> sent out 1st using the Direct approach, if it fails then fall back to
> the smart host.
> 
> Something like /etc/host.conf
> 
> user$ cat host.conf 
> order hosts,bind
> 
> pseudo code :
> if [check if it's a local address ]; then
> 	pass to local sendmail
> elif [check if we can send direct to MX ]
> 	pass to sendmail for direct MX
> else # when all else fails
>        pass to smart host for relay

If I remember correctly there is no such fallback order.
Do you use different mail addresses at work and at home? Then you could
use smarttable. Else I would suggest not using the smart_host definition
in the sendmail.mc file, but to use the mailertable instead. That makes
switching a bit easier: you don't need to restart the Sendmail daemon
because you don't change the sendmail.mc/.cf file but the mailtertable
hashed map file: edit the mailertable file and run "make -C /etc/mail"
and your change takes place immediately. See

http://www.sendmail.org/m4/mailertables.html

on how to set the entry for your smart host. To deactivate simply put a
# in front of it to directly speak to the recipient MTAs.

> Ow Mun Heng

Alexander


-- 
Alexander Dalloz | Enger, Germany | GPG key 1024D/ED695653 1999-07-13
Fedora GNU/Linux Core 2 (Tettnang) kernel 2.6.7-1.494.2.2smp 
Serendipity 20:18:18 up 12 days, 13:45, load average: 0.16, 0.18, 0.12 
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