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

Download Free Spam Blocker News

New Free Anti Spam Blocker Tool: Webmasters and Bloggers Fight Back

Manchester, NH (PRWEB) December 9, 2008 -- http://www.SpamDisapppears.com has launched with a free anti spam blocker tool to help any webmaster protect their web sites from being violated by email...

Read more...

---

Beware of Fake Antivirus Products, According to BitDefender Labs ... - PR-CANADA.net (press release)

Beware of Fake Antivirus Products, According to BitDefender Labs ... PR-CANADA.net (press release), Montenegro - Dec 8, 2008 "However, spam and webpages are just part of the problem, which is why it is essential users ensure their computers are malware and virus free by running ...

Read more...

---

Refinance As Low As 5.48% - Sponsored Link

Ad - Compare Up to 4 Free Offers. Home Refinance Inquiries Only.

Read more...

---

Men's Basketball Opens BIG EAST Action at Marquette

its lowest shooting percentage since shooting 26.7 percent at Connecticut on March 9, 2008. Cincinnati hit 18-of-23 free throw attempts compared to Memphis hitting 10-of-18 attempts from the charity stripe. UCs bench averaged 32.4 bench points per game

Read more...

---

Wells, BofA complete big acquisitions

than 6,600 outlets in 39 states and Washington, D.C. Wells and Wachovia customers will immediately have free use of both banks' ATMs. San Francisco-based Wells (NYSE: WFC) agreed to buy Wachovia on Oct. 3, topping a bid by Citigroup Inc. (NYSE: C) for

Read more...

---