exim host_lookup feature

[Mario Olimpio de Menezes <mario@curiango.ipen.br>]

Hi,

	I'm trying to understand the above feature on exim config.
	Is it supposed to block unqualified senders, e.g., people using
ppp connection w/o reverse dns?
	If it's not, is there such option?
	More, is this an appropriate measure to reduce spam from
adsl/ppp/isdn connections without reverse dns registered?
	Comments on this subject are welcome.
	Thanks,

Mario O.de Menezes            "Many are the plans in a man's heart, but
    IPEN-CNEN/SP                 is the Lord's purpose that prevails"
http://curiango.ipen.br/~mario                 Prov. 19.21