I never used Qmail, so I won't comment on it, but I will say I absolutely consider djbdns narrow in scope as well (before accounting the Unix approach, utilized perhaps even more than in MaraDNS, to break that already narrowed scope down into even more focused binaries).

I had believed (and continue to hold) DNS software containing, e.g., an authoritative DNS server which lacks native TCP or DNSSEC support falls squarely into the "narrowly scoped" bucket and would appreciate if you'd not try to decide my opinion for me on any given project in the future.