by Karen Fegarty

More than 40% of all emails within your marketing campaign are not being delivered. You may not even be aware of this, as many ISPs will not send back a bounce message. If you are sending messages to AOL customers, AOL is now blocking more than 80% of the messages that come into their servers.

One of the reasons this is occurring is your IP or domain may be blacklisted. All major ISPs and many corporate email systems now check against blacklists and refuse to deliver emails that come from a blacklisted IP.

But what exactly is a blacklist?

DNS blacklists are lists of domains and IPs known to originate spam. Many anti-spam software programs used by corporations and ISPs use these lists to control spam by refusing email originating from one of these blacklisted domains or blacklisted IPs.

Unfortunately there are as many instances of false positives as there are few checks and little objectivity when listing a particular IP. For a blacklist to know that a domain is sending spam, the offence must be reported. It may take only one report via a web form for you to be blacklisted.

You can be listed maliciously by one complaint of a client or a competitor. Many blacklists list not only the IP that is suspected as spamming, but list any IPs in the range of addresses. If someone using the same Internet provider as you is accused of spamming and is placed on a blacklist, you may be listed as well.

DNS blacklists are usually maintained by anti-spam organizations or by individuals.

What are some of the most popular blacklists that ISPs are using?

Some of these include:

MAPS - http://www.mail-abuse.com/
Spam Cop - http://www.spamcop.net/
SpamHaus - http://www.spamhaus.org/
SPEWS.org - http://www.spews.org/
ORDB.org - http://www.ordb.org/

How do I know if I am on a blacklist?

Unfortunately, you can't be 100% sure. You may be on someone's blacklist and not even know it. There are, however, ways to check most of the blacklists.

One way is to check your server log when sending your campaigns. You will often see an email bounce notice indicating the message has bounced because you are on a particular blacklist.

Many of the major blacklists also allow you to enter your IP into a form on their site. These checks tell you whether you appear, or not, on their blacklist.

A useful tool is the Blacklist Monitor. It automatically checks your IP against most of the major blacklists and tells you the ones you are blacklisted on. It also helps you get removed. All your IPs are constantly monitored for any changes, blacklistings, or delistings.

But what is a whitelist and how can this help?

Many corporations and ISPs create whitelists. This is a list of trusted IP addresses they feel confident will not send spam to their customers. If your IP is listed on a particular whitelist, your email messages will be delivered to the destination email address. It is important for reputable marketers to work with the major ISPs, such as AOL, to ensure they are on their whitelist. For most it can be a lengthy process, but well worth the efforts.

Other third-party email certification programs now exist. Bonded sender is one such agency. By joining Bonded Sender, senders improve deliverability rates and differentiate their brand. Senders go through a formal application process, adhere to email standards, and post a bond against potential complaints. Major ISPs such as MSN/Hotmail now check against Bonded Sender's whitelist and allow these email to pass.

Knowing if you are on a blacklist, getting removed if you are, and getting established on whitelists is critical. Remember, the more messages delivered, the more sales.

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Author Karen Fegarty is with Mailworkz, the creator of Blacklist Monitor - an advanced service that continuously checks all the major blacklists. Don't be treated unfairly. Keep a handle on who may have you blacklisted. Get a free trial and find out more at http://www.blacklistmonitor.com.