[Mimedefang] RBL and DNS lookups

[Jonas Eckerman]

Daniel Aquino wrote:

>> Yes, there is system overhead in performing RBL checks.

> I'm just worried about the thousands of emails that come in all the
> time that are spam...  An they sit around in your memory timing out
> because of dns lookups...

Has this actually happened to you or someone you know, or are you 
just worried that it might happen?

We had problem with DNS timeouts for a short while a couple of 
years ago after an increase in our mail load. After installing a 
caching DNS proxy in the same machine as 
Sendmail+MIMEDefang+SpamAssassin the problem went away.

> Would I need a special dns daemon hanging around for doing just this task ?

That depends entirely on you system load and how your existing 
DNS system and network handles it.

You are the only one here who knows wether your mail system 
suffers from DNS timeouts or not.

>> in some cases, I run local mirrors of the entire RBL.

> How do you achieve this?

I don't know how he does it, but the most common way seems to me 
to be to use rsync or zone transfers to download the data and 
then use it in a local DNS server. (Note, I don't do this myself, 
so I may well be a bit off in this assumption.)

Regards
/Jonas

-- 
Jonas Eckerman, FSDB & Fruktträdet
http://whatever.frukt.org/
http://www.fsdb.org/
http://www.frukt.org/