Network configuration questions

[Cory Echols <CEchols@aflacrd.com>]

After a move I went from a cable modem w/static ip to DSL with dhcp.  I'm
trying to figure out what configuration
changes to make to my machine.

Since this is a dhcp machine now, what should I put in 
/etc/hostname?  I tried putting a "hostname" in there and
defining "hostname" as 127.0.0.1 in /etc/hosts, but 
sendmail puts errors in my mail logs saying "I can't 
qualify "hostname". Using short name instead".  I'm 
assuming that this may cause problems.  Email from my 
machine may get filtered by anti-spam bots, for example.

I've also noticed that sendmail puts my old machine name
(from my previous static ip cable modem configuration) in
the "From" line (not "From:") in outgoing email.  This
is probably a bad thing too.  How can I fix that?

This also brings up the bigger question of where the
machine's hostname and domain name are actually defined.
I had always thought the hostname was set in 
/etc/hostname and the domain name was set by the "search"
line in /etc/resolv.conf.  My recent experience with
sendmail leads me to think otherwise, however.

BTW:  I am considering switching to exim.  Does it have
features that would help it play nicer on dhcp configured
machines?

Thanks in advance for the help.

--
Cory T. Echols
cechols@aflacrd.com