Glossary of Terms
- Key technique used in anti-SPAM measures.
- Secondary technique used in anti-SPAM measures.
- Currently in place but not seen to be used for anti-SPAM measures
Bounce Rate - This metric is composed from the number of non-deliverable unknown recipient email addresses that a mailer is attempting to deliver to a specific ISP. Many ISPs will block all or some of your email campaigns based upon your bounce rate.
Bottom Line: In order to avoid deliverability problems the percentage of undeliverable email addresses sent to any ISP should never be above 5%.
Challenge / Response - This anti-SPAM measure seeks to protect recipient inboxes from SPAM by returning a "challenge" email to the original email sender that asks a question that only a human can answer, usually protected by some type of wavy text that a machine could not read. Once the original sender returns the challenge, their email address will be added to the recipients address book and subsequent email campaigns will be delivered to the inbox.
Bottom Line: It is recommended that email senders looking for maximum deliverability assign the task of returning challenge / response emails to a customer service rep position. It should also be noted that mailers should maintain a consistent From Address. Changing your From Address will result in decreased deliverability as you will have to respond to all challenges again.
Commercial Blacklists - Commercial Blacklists include lists of IP Addresses maintained by the ISP itself as well as lists maintained by commercial third-parties. The biggest commercial blacklist provider is Brightmail, which was acquired by Symantec in 2004. Brightmail is a multi-layer content filter that leverages over 17 different technolo- gies, including SPAM signatures, heuristics, reputation filters, language identification, and many proprietary methods. Many ISPs license Brightmail's technology and use it as a method for protecting their subscribers' inboxes. If you find your campaigns being blocked at several different ISPs it could be due to the fact that you were placed on Brightmail's blacklist.
Commercial Blacklists - (con’t) It should also be noted that Symantec has rolled out several anti-SPAM software applications and email appliances that use Brightmail. These offerings are geared towards businesses and are being implemented by corporate IT administrators to protect many corporate inboxes.
Bottom Line: Mailers following best practices for permission and privacy will most likely not find themselves on Commercial Blacklists. Employing practices of unconfirmed opt-in, email appending and/or list rental could result in deliverability problems due to commercial blacklists.
Connection Filtering - While each ISP maintains different thresholds for the number of concurrent connections, one thing is certain, ISPs do not appreciate being bombarded by mailers trying to deliver email as fast as possible. Keeping concurrent SMTP connections per domain below 10 will keep you out of trouble with most ISPs. The best way to know if you have a connection filtering problem is to search through your bounce or SMTP logs looking for the string "too many." This simple technique will uncover other issues such as too many complaints, too many bounces, etc.
Bottom Line: Keep concurrent connections per domain below 10 to avoid deliverability problems.
Content Filtering - For permission mailers employing best practices for email address acquisition, content filtering will most likely be your biggest challenge. Content/filtering entails an email system blocks emails containing words that are offensive or often found in SPAM or bulk email. Many corporate email administrators also maintain their own list of words to block as well. We recommend several techniques to avoid content filters falsely identifying your permission-based mail as SPAM. Those techniques include:
a. Ask recipients to add your address to the address book b. Convert "SPAMMY words" such as "unsubscribe" or "offers" to graphics.
Bottom Line: At this time there is no silver bullet that will get your messages past content filters. Use common sense and employ tools such as the Listrak "SPAM Score" feature to pre-screen your content. Additionally, ask your recipients to white list your mailing address.
DNS Configuration - This item primarily pertains to AOL. If you do not have reverse DNS setup correctly for your mail server, AOL will not deliver your message. You can find a more complete description of reverse DNS at: http://www.dnsstuff.com/info/revdns.htm
Bottom Line: If you are outsourcing your email campaigns to an ASP this is something that you don't have to worry about. If you are running your campaigns in-house, you will want to double check with your IT group to make sure reverse DNS is configured properly for your mail servers.
Email Sender Authentication - Email Authentication seeks to solve the overlying security problem with email which is the fact that Person A can send an email to Person B and purport to be Person C. This happens because there is no inherent security model built into sending email.
To combat this issue, several groups have come together in the past year to enact new technical standards that attempt to curb SPAM and fraudulent email. These groups include the open source community, Microsoft, AOL, Yahoo!, Cisco and many others. You might have heard of these initiatives. They go by names such as SPF, Sender ID, DomainKeys and CII. All of these technologies fall under the umbrella of Email Authentication.
Bottom Line: Much to our disappointment we have not seen a noticeable increase in deliverability by publishing an SPF record. Of course, it's always advisable to publish an SPF record to protect your domain from phishing and fraud. However, we would like to see email receivers, such as the ISPs outlined in this document, assign email sent from email authenticated domains a slightly lower "SPAM score" than email sent from non-email authenticated domains.
Non-commercial Blacklists - The Internet community has operated several free public blacklists that have gained in popularity over the past few years. Primarily small to medium sized companies or ISPs are subscribing to these free services. Our findings show that while the majority of major ISPs do not subscribe to these blacklists, they should not be overlooked, especially for anyone mailing to B2B lists.
User Complaints - When mailing to the top ISPs mentioned in this whitepaper, this criteria is by far the most important metric. Almost all of the top ISPs have some form of gathering complaint data from their users. As email authentication standards evolve and eventually become ubiquitous, complaint data will be a major factor determining whether your mail gets delivered.
Bottom Line: If you want to get your messages delivered to the inbox you have to play by the rules of permission. The lower the permission level, the higher the complaint rate. The higher the complaint rate the better chance your message will end up filtered or not delivered it all.
Bonded Sender - Bonded Sender is the leading third-party email certification program. Participating Bonded Sender mailers post a monetary bond as well as pay an administrative fee to have their mail delivered unfiltered to over 34,000 ISPs, corporations and universities - the largest receiver of which is Hotmail/MSN. By joining Bonded Sender, senders improve deliverability rates. ISP's and other email receivers benefit by avoiding the risk of inadvertently deleting email their users want. Originally founded by Ironport Systems, Bonded Sender is now under the direction of Return Path.
Habeas - Operating in a similar capacity as Bonded Sender, Habeas offers a comprehensive suite of services for volume email senders of legitimate, business-critical email. Habeas provides certification, classification, legislation compliance monitoring, delivery-enhancement services, and mediation services to help resolve disputes with ISPs.
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