The -d8.5 debugging switch causes the getcanonname(3) routine to print the hostname it is trying to fully qualify. It shows the name with the local domain appended, without the local domain appended, and at each step in between. Each try is printed as:

dns_getcanonname: trying host.domain (type) 

Here, the type is the type of lookup and is either A, AAAA, or MX. (Prior to V8.12, the type could also include ANY).