FAQs of Life

RBL (Real-time black lists) are very effective spam blocking mechanism.  However, like any spam prevention solution, it is far from perfect and legitimate email can be blocked as well.  An RBL is a list of IP addresses that an email server will not accept email from.  This is very effective as a spam blocking mechanism but can also be an issue for small businesses that have internal email servers since they often, through no fault of their own, are included on the RBL lists.  With the rise of spam originating from spyware and virus infected home PCs, RBLs almost always block email if it is sent directly from an IP address “known” to be a residential broadband range.  This is terrific concept except it is a huge under taking to maintain an accurate list of residential broadband IP addresses. RBLs are also know to add large ranges of IP addresses to their list if they detect spam activity from a single IP address within that range.  And unfortunately, the consensus attitude of the organizations that maintain most RBLs is “your were blocked for a reason, prove to us that you don’t send spam, we then might unblock you if we believe you.”

If you can’t tell from my tone, I don’t agree with this approach for preventing spam. If you are in a position to decide to use a RBL to block spam, please thoroughly research the various solutions and use one that has a mechanism for legitimate users to easily get themselves removed from the list.  There are some lists that charge a fee to be removed from their list (highly suspect!).

Here are some online tools that will check to see if your server is listed on an RBL

http://www.dnsstuff.com
http://www.robtex.com/rbl

Here’s a link to get removed from AT&T’s RBL
http://worldnet.att.net/general-info/bls_info/block_inquiry.html
And you need it, here’s a phone number for AT&T abuse department (to use if their online system doesn’t get you removed)

1-800-648-1626 option 1

One of the most common questions that I get is about email “bounces” - why did this message get returned?? The funny part is, the more time I spend managing email servers, the more surprised I am that any email ever gets to the intended recipients! That said, we can usually figure out why the message didn’t make it through from the information in the bounce message.
Here’s a few Non Delivery Reports (NDR) that different customers have received in the past couple of weeks

goodemail.server.com #5.3.0 smtp;553 5.3.0 nlpi050,DNSBL:521< 65.6x.1xx.7x>_is_blocked.__See_http://www.att.net/bls_rbl/_for_information.>

goodemail.server.com #5.5.0 smtp;591 recipient@idontknowtheirblockingemailtome.com your host [64.1xx.2xx.2xx] is blacklisted by feb.spamlab.com. No mail will be accepted>

goodemail.server.com #5.5.0 smtp;550 lotsofemail@recipient.net…User account is overquota

In many cases, unless you’re the email administrator, you may not be able to resolve the problem but you’ll never know unless you read the error message. While these error messages are not “user-friendly” as computer error messages go, they are far from cryptic. The words “blocked” and “overquota” should give you a clue on what the problem is. If an email server is blocking your email, you’ll need to get the administrator (either your admin or the recipients) involved. However if you see an “overquota” or “mail box is over allowed size” message, you can often solve the problem by phoning the recipient and having them delete some of the email stored on their server!

Many times, there will be links listed in the error message that have more information about why the email didn’t go through. In the first NDR listed above, the sender’s email server was listed on a “real-time blacklist” (RBL - a spam prevention mechanism - a topic for another post) and you can use the link to get your server removed from the list.