[lug] sendmail from cable/dhcp

[Neal McBurnett]

For years I've had no trouble with a standard redhat configuration,
sending email via mutt and a local sendmail on my machine, directly to
the recipients.  The ISP is attbi, but I don't use their smtp server.

I.e. I'm on a dhcp connection.  But that connection hardly every
changes IP address because the machine is up all the time.

I did have to do one thing to make this work: add my DNS name to
my /etc/hosts file for 127.0.0.1:

 127.0.0.1       12-253-85-111.client.attbi.com lock localhost.localdomain localhost

For the first time in many months I got a new DHCP address 
a few weeks ago, but things continued to work.

Then I rebooted a few days ago, and now mail to certain places
(like colorado.edu) is not working.  I get bounces with this message

 451 4.1.8 Domain of sender address neal at 12-253-85-111.client.attbi.com does not resolve
 Warning: message still undelivered after 4 hours
 Will keep trying until message is 5 days old

and it keeps trying every hour with the same error.  That started
yesterday.


There were at least two problems the first time I saw this.  First, I
hadn't changed the hosts file when I got the new IP address via DHCP,
so I was claiming to be from the wrong place.

Second, from another machine at CU, I actually verified that the
"host" command couldn't find the old address
 12-253-85-111.client.attbi.com

Could be that no one was using it at that point in time....

So I changed the address in /etc/hosts and progressively tried
 service sendmail restart
 service network restart
 reboot

I've now gotten thru to one of the places that was refusing my
mail, but CU still isn't taking it.


I have a few questions:

 1) Any insight on fixing this particular problem?  I'd like to send
 email directly because then I can look at the logs to see exactly
 when the mail was delivered to the recipient's machine, and I can
 turn on opportunistic encryption via SSL, and other useful features.

 2) How do most people (e.g. Mutt users) send mail from boxes that use
 DHCP?  Changing the /etc/hosts file is a royal pain.  I would imagine
 that it would be common for people to use some sort of sendmail.cf
 that just directs all mail to the smtp service at mail.attbi.com, but
 I don't see instructions for doing that in the redhat documentation
 at

 http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/ref-guide/s1-email-sendmail.html

 3) I've also run into at least one site that just won't take email
 directly from a cable box, obviously for spam reasons.  Is there a
 way to tell sendmail about such sites so that it uses direct
 connections, (encrypting when possible) to most places, but routes
 mail thru mail.attbi.com for the rest?

Thanks,

Neal McBurnett                 http://bcn.boulder.co.us/~neal/
GPG/PGP signed and/or sealed mail encouraged.  Keyid: 2C9EBA60