This is why slow DNS often expanded to 3-4x as long as the expected
timeout value; we make a handful of calls in succession, assuming
that the cache was effective in an earlier stage.
We now cache errors for 5 minutes by default, and it can be configured
as desired.
refs: https://github.com/KumoCorp/kumomta/issues/325
This function returns MX information, including the computed site_name.
Update the queue example to show how to use it to populate the SITE_OF
map used in that example.
This commit switches to using the `Name` type under the covers to ensure
that we use canonical names for our cache keys.
Wez Furlong
ncai