- The name of a mail exchanger, the forwards of whose domains we should
- ignore. For example, if one mail exchanger, mx1.example.com, has
- strict spam filtering, it may be acceptable to have remote forwarding
- for domains that have mx1.example.com as their sole mail exchanger (MX
- record). In that case, you might want to exclude those domains from
- the report by naming mx1.example.com here.