"Sender domain must exist" problem with daily output emails

I set up a vanilla OpenBSD 3.2 box to host CVS for a development project. I want to receive the 'daily output' emails and cron job results at my regular email address. So I aliased root to my username in the /etc/mail/aliases file and installed a .forward file listing my regular email address. The box gets its networking info via dhcp from a netgear router connected to a cable modem.

I get emails alright, but they are "Returned mail", with the following:

• The following addresses had permanent fatal errors ----- ... (reason: 501 <root@fasteddie.sttls1.wa.home.com >... Sender domain must exist)

where 'fasteddie' is the name I gave the OBSD box at setup and 'sttls1.wa.home.com' is a domain name that the cable company must supply to my netgear router which is passed along to the OBSD box via DHCP. Needless to say fasteddie.sttls1.wa.home.com is not a legitimate domain name!

How do I configure the box to send mail that isn't returned? Thanks! Received on Tue Jan 21 21:18:21 2003