ares will to look in /etc/hosts if it fails to find the entry via a DNS lookup
It will look in /etc/inet/hosts if you have ETC_INET defined.
If you put the following line into /etc/resolv.conf:
lookup f b
you are telling ares to look in host (f)ile before DNS(b) servers.
The rutil library appears to have some level of support for ENUM queries, as do the DNS related classes under resip/stack. This space is reserved for an explanation of the current state of affairs with regards to resiprocate's ENUM support.