- /* Do the lookup and sort out the result. We use the special
- lookup function that knows about pseudo types like "zns". If the lookup
- fails, continue with the next domain. */
+ /* Do the lookup and sort out the result. There are two special types that
+ are handled specially: T_ZNS and T_MXH. The former is handled in a special
+ lookup function so that the facility could be used from other parts of the
+ Exim code. The latter affects only what happens later on in this function,
+ but for tidiness it is handled in a similar way. If the lookup fails,
+ continue with the next domain. */