in transport context, after the attempt, and per-recipient. The latter type
is per host attempted. The event data is the error message, and the errno
information encodes the lookup type (A vs. MX) used for the (first) host,
in transport context, after the attempt, and per-recipient. The latter type
is per host attempted. The event data is the error message, and the errno
information encodes the lookup type (A vs. MX) used for the (first) host,