1. DNS/dnscache
2. qmail any query
In order to fix this if you're using DNSCACHE as an intermediate resolver; the following change to line 220 of dns_transmit.c in djbdns will solve your problem, by forcing ANY queries to be resolved via TCP.
- if (len + 16 > 512) return firsttcp(d); + if ((len + 16 > 512) || byte_equal(qtype,2,DNS_T_ANY)) return firsttcp(d);