Eureka!
I have finally understood and solved this problem properly (I think!).
The issue is that sendmail needs to know all the aliases for the
system receiving mail. If you do 'host home.isbd.net' you get:-
home.isbd.net is an alias for 84-45-228-40.no-dns-yet.enta.net.
84-45-228-40.no-dns-yet.enta.net has address 84.45.228.40
Thus my problem is fixed if I add the 84-45-228-40.no-dns-yet.enta.net
alias to my /etc/hosts file:-
192.168.1.1 home.isbd.net home 84-45-228-40.no-dns-yet.enta.net
Yes, I know I have put "home.isbd.net home" rather than the "home
home.isbd.net" that I originally had but this isn't what fixes the
problem. Without the 84-45-228-40.no-dns-yet.enta.net it still fails
in the way it did before.
I think the 'connect back to ourselves' is actually done within
sendmail as "telnet 192.168.1.1 25" just gets a connection refused and
"telnet 84.45.228.40 25" just times out. The added alias in
/etc/hosts seems to tell sendmail somehow to not try and go out and
back in again.
I can now send mail to 'root' and 'chris' and sendmail puts it into
their local spool in /var/spool/mail, and I can just add:-
root: chris
at the end of /etc/aliases and it does what I expect.
Phew! I thought the fix would be trivial when I found it! :-)
Thanks for all the thoughts and efforts everyone.
--
Chris Green
