The next two lines are concerned with &'ident'& callbacks, as defined by RFC
1413 (hence their names):
+.new
.code
rfc1413_hosts = *
rfc1413_query_timeout = 0s
.endd
+.wen
These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
Few hosts offer RFC1413 service these days; calls have to be
terminated by a timeout and this needlessly delays the startup