Things You Should Know Before Using DNS Block Lists

DNS block lists are easy to include into most mail servers. They are a very effective and efficient server side tool to help keeping spam out of your systems. As the name implies they use domain name servers to transmit the information whether mails from a distinct mail server should be accepted or rejected.

Sometimes they are too effective. It can happen that a mail server is listed on a block list wrongfully. This can lead to a situation where your mail server will reject mails that you wanted to receive. The biggest problem with block lists is that you have to trust somebody else to take the right decision which mails to accept and which ones to reject.

So how useful are DNS block lists after evaluating the pros and cons? They can be very useful to lower the overall CPU usage of your anti spam strategy. It is advisable to use a small number of carefully chosen blocklists. If you are using a block list, subscribe to the mailing list or newsletter of the organization who runs the block list. That way you will take note of any problems that the block list may have and you will be informed if it gets shut down. DNS blocklists should never be your only strategy against spam. They should be combined with other mechanisms to help keeping spam out of your inbox.

There are some things you should consider before implementing DNS block lists in your anti spam strategy. If you reject a connection from a mail server because it is listed in a block list, return a detailed error message. This enables the admin of a mail server that gets listed wrongfully to see why the mails get rejected and to act accordingly.

If your mail server software allows to select the order of different sender or client restrictions be sure to put DNS blacklists after SMTP authentication. This enables your co-workers (and your customers if you are in the ISP business) to send their mails even if they come from a dial-in IP address that is listed in a block list.

You should consider using DNS block lists for scoring instead of blocking if your mail server has enough resources (CPU, IO, traffic). That would mean to use the block lists in a program like spamassassin that gives points for different criteria of a message and considers it as spam if it surpasses a certain number of points. That way the chances for false positives are lower because a message is not rejected if the sending server is on a single block list only. The message will get rejected if there are other signs of spam.

Huge indexes of available DNS block lists can be found at www.moensted.dk/spam/ and www.declude.com.

Spam Videos

Dns Block List Headlines

Dutch ISPs Don't Need to Block Pirate Bay - NewTeeVee (blog)

Dutch ISPs Don't Need to Block Pirate Bay NewTeeVee (blog) Dutch anti-piracy organization BREIN had asked the court to block the torrent site at the DNS level, with the provision to update the block list with new IP ... and more »

Read more...

---

StreamSend Names Top 12 Email "Don'ts"/Email Analyzer Tool Cleans Emails Pre ... - PR-USA.net (press release)

StreamSend Names Top 12 Email "Don'ts"/Email Analyzer Tool Cleans Emails Pre ... PR-USA.net (press release) SPF records, included in the senders' DNS, have become a key tool in preventing 'from address' forgery. Keep your HTML code simple. ... and more »

Read more...

---

Don't just build business-IT alignment, map it - ITWorld Canada

Don't just build business-IT alignment, map it ITWorld Canada Hosted DNS service includes IP address managementBy: Howard Solomon (15 Jul 2010)For some companies, a hosted domain name system service (DNS) is the only ... and more »

Read more...

---

How to set up a proxy server - TechRadar UK

TechRadar UK

How to set up a proxy server TechRadar UK Proxy servers are often used to block content, and FreeProxy does this admirably via ban lists. Click 'Ban Lists' on the FreeProxy Control Centre and the ...

Read more...

---

D-Link DIR-685 Xtreme N Storage Router - PC World India

D-Link DIR-685 Xtreme N Storage Router PC World India For home users whose external IP address would keep changing, hosting a publicly accessible Internet server is made possible via support for Dynamic DNS ...

Read more...

---