I have in my .mc:

    define(`confBIND_OPTS',`-DNSRCH -DEFNAMES')
    define(`confDOMAIN_NAME',`bsd.laptop')

    FEATURE(nocanonify)dnl
    FEATURE(accept_unresolvable_domains)dnl
    FEATURE(accept_unqualified_senders)dnl

I don't remember what the top two do, but most of the
sendmail-using-ppp FAQs seem to recommend them, and they
don't seem to hurt anything.

-- 
"Source code in files. How quaint." - Kent Beck
"Maybe this world is another planet's Hell." - Aldous Huxley