Re: sender_host_reject_bydns

>> The one disadvantage that I can see, is that people outside your site may be
>> able to see the blacklist data. The Spammers may then use this to create new
>> accounts which aren't (yet) blocked.
> I think the second point is particularly valid. However, you could try
> running a private Zone to keep the information local. Anyway, I will
> certainly look into the facility, because I can see other uses for it.

Is the concern of allowing explicit lookup "Am I blocked",
or is it SPAMmers doing a Zone Xfer ? The latter can be blocked.