Sendmail reject non-extant hosts? RFC1123

[Dan Nelson]

In the last episode (Jul 20), Kevin Kinsey, DaleCo, S.P. said:
> I'm not happy that Sendmail is allowing connections from non-
> existent hosts (i.e., spammers...)
> 
> So, how do I tell Sendmail that if a host doesn't exist, (i.e.
> d3kr890d.129ddk.org) I don't want to talk to it...

This works for me:
http://www.sendmail.org/~ca/email/chk-810.html#810UNRESOLVIP

LOCAL_RULESETS
SLocal_check_rcpt
# check client name: did it resolve?
R$*			$: < $&{client_resolve} >
R<TEMP>			$#error $@ 4.7.1 $: "450 Cannot resolve PTR record for " $&{client_addr}
R<FORGED>		$#error $@ 5.7.1 $: "550 IP name possibly forged " $&{client_name}
R<FAIL>			$#error $@ 5.7.1 $: "550 IP name lookup failed " $&{client_name}

-- 
	Dan Nelson
	dnelson at allantgroup.com