please criticise simple fix for m1=>attbi transition

[root]

I am trying to deal with the mediaone==>attbi mess.
My setup is a firewall (horne.ne.mediaone.net) that forwards all
mail to a "smart host" behind the firewall.

In three attempts (email, phone) I have not encountered anyone at attbi
who can say whether xxx.ne.mediaone.net will ==> xxx.attbi.net.
I am assuming not.

I went to dyndns.org (thanks)  and set
up a new hostname, horne.homelinux.net, pointing at my
(mostly static) IP.   Things seemed to work, to first
order.

To get email working I did the following hack - 
in sendmail.cf on the firewall, I added a hostname so -- 

Cwlocalhost horne.homelinux.net

(entire domain is masqueraded)

Now mail to eg steve at horne.homelinux.net gets to me. 

To fix outgoing mail to have the correct domain, I
changed sendmail.cf on the smart host as follows:

DMhorne.ne.mediaone.net
to 
DMhorne.homelinux.net

A couple quick tests seemed to do the right thing.

Is this sufficient, or is there more to do?
It surprised me that I didn't have to change the "domain" line
in resolv.conf -- it kept being overwritten by the dhcp script
so I left it alone.

I don't run a web server - just family email and ssh.

                        Thanks,
                                        Steve