Topica's Blog

Part 1: How Spam Filters Work

This is Part 2: What is my External Reputation?

Part 3: How to Increase Open Rates and Decrease Complaints – coming tomorrow!

In my post yesterday, I described spam filters as a sort of black box. Emails come in and emails come out in one of two directions, either to the inbox or to junk.  Technically, there is a small third possibility of the emails actually being deleted by the spam filter and never seeing the day of light in either the junk or inbox. However, this is almost a non-issue for legitimate senders.

The exact internal workings of these black boxes are closely guarded industry secrets and every ISP is constantly tweaking theirs to give their customers the absolute best spam filtering technology. However, as I mentioned, just because we don’t know the exact internal workings of the black box, doesn’t mean we can’t do everything to optimize our chance of getting through these filters and into the inbox. This is what makes deliverability more of an art then a science.

As I mentioned yesterday, it’s easy to think of these filters examining your email on three different layers. The first one is the actual makeup of your email and deals with a lot of content-based rules. To get an overview of some of the most important ones, please read Part 1. The second layer is what I refer to as your external reputation. This deals with everything the filter can assess about you as a sender based on outside information. This is in contrast to the topic of tomorrow’s post on internal reputation, which deals with the information unique to the ISP (e.g. how many of their users complained about your last campaign).

Now when it comes to your external reputation of your mailings, one of the first things the ISP’s will examine is how you sent the message. Throughout the years, many best practices have become standard in order to distinguish SPAMMERs from legitimate senders. These mostly revolve around authentication (i.e. being who you claim to be). Things that fall into this category are rather technical and are usually handled by an experienced systems administrator or an outsourced email marketing company. Here is a quick summary of the most commonly used tools.

• Reverse DNS – These associate your sending IP with a domain name that matches up with your sending address
• SPF Records – Published specifications that essentially limit who can send out from your domain
• Sender ID – Very similar to SPF Records and primarily used by Microsoft domains (Hotmail, MSN, Live.net, etc)
• Domain Keys Identified Mail – Another email authentication method most commonly used by Yahoo and Gmail

It is important to note that having any of these does not automatically make you a good guy to the ISP’s. However, not having one will make you seem like a spammer.

When sending a large volume of mail, a hard number to pin down for most ISP’s as anything coming in over 500 can be perceived as a large volume, the way your mail server attempts to connect to their mail servers will also be scrutinized. They will examine how many connections you are attempting to establish at once and what is the volume going out on your sending IP’s. Also, a lot of times an ISP can’t accept all their incoming messages at once so they will often defer the delivery until a little later. They will look at how your servers treat deferrals. They want to see how often you retry and for how long you keep retrying. In fact, ISP’s have been to known to intentionally defer emails to weed out bad senders. On top of all this, each ISP has its own specifications and not all of them are published or even common knowledge.

As you can see there is a lot to keep track of just to keep yourself from being viewed as a spammer. Likewise it doesn’t help that each ISP has its own specifications and that they can easily change. Of course I’m biased because I work in the industry, but this is one of the strongest reasons to (warning: shameless plug ahead) outsource your email-marketing to a solid email marketing company or to build an incredibly robust in-house system and at least keep a derivability consultant on hand. Believe me, you will be happier knowing that not only do you have someone dedicated to staying current on all the best practices especially BUT in the dreaded case  something does go wrong, such as a block or a black-listing, you have someone who can help you deal with the issue in the fastest way possible.

Tomorrow, I will move into the realm of what happens once your email is delivered and how it will affect your future deliverability. The post will not be as technical and will include tips and guidelines to help you get your best open rates, minimize bounces and avoid complaints. Metrics everyone, including the ISP’s, want to see.

As always, please feel free to follow up in the comment section and I’d be more than happy to directly respond to you. Also, to wrap-up the week we will be doing our Derivability webinar live on Friday September 24 at 2pm EST. Sign up and bring your best questions and suggestions or just to hear what others have to say. Thank you.

Andrei

Filed under: About Topica, Best Practices, Deliverability Days, Do's and Don'ts