help with T_ANY

[cowbert at gmail.com]

As you all know, djb's mail server qmail makes a T_ANY query before
making any others. My problem is somehow my bind 9.3.2 authoritative
will often only return NS RRs to resolvers that drop other records of
my zone from their cache (specifically, the nameservers at yahoo.com).
This causes yahoo's qmail to bounce with "CNAME lookup timed out" a
lot, which is unacceptable for us. It is my understanding that T_ANY
will only return what's cached, but if I am incorrect about this how do
I fix my nameserver so that the wildcard query will return at the very
least, the MX record for the zone (besides increasing TTL)?

some details of the zone:
foo.bar. 14400 IN     SOA     ns.foo.bar email.foo.bar 2006102016 3600
3600 604800 14400