Two Worlds of Email Deliverability

If your email is being filtered, you can either make it more wanted by recipients or try to get it past the filters with technical tricks. Those two approaches lead to two very different "worlds" of deliverability, and only the first one works over time.

World 1: working with the mailbox providers

Here your aim matches the providers' aim: mail that recipients want and expect, which is the mail providers are trying to deliver to the Inbox.

Two conditions define that mail:

• Wanted: it gives recipients something they value.
• Expected: recipients recognize it, because they signed up or already have a business relationship with your brand.

A provider cannot see into its users' minds, but it can observe their behaviour at scale, across tens of thousands of mailboxes, and that tells it more than asking would. Complaints and engagement carry the most weight: how many recipients mark a message as spam, how many open and read it, how many delete it unread, and how long they spend on it. Filtering algorithms turn those measurements into a verdict on whether your mail is wanted and expected.

Behaviour is not the only input. Providers also examine content, where particular words or phrasing can push a message toward spam filtering, and technical sending details such as the number of connections you open, email authentication and warm-up schedules.

Senders in this world send plainly and do not look for technical loopholes to "game" the system. Providers exist to deliver mail their users welcome, so in a program built on wanted and expected email the rest typically follows. Delivery problems still happen, and they are typically fixable.

Open rates of 5% to 20% or higher are common here, and the target is the Inbox.

World 2: working against the mailbox providers

Here senders try to trick spam filters into accepting or delivering mail that recipients neither want nor expect.

Many senders arrive here without meaning to. Suppose your mail draws a lot of complaints or very little engagement, and providers have started filtering it. You have two possible responses:

• (A) Look into the program itself: identify where the complaints or spam-trap hits come from and remove that cause, so recipients want and expect the mail more. That response keeps you in World 1.
• (B) Leave the underlying cause in place and put all the effort into workarounds, such as spreading mail over many IP addresses so none attracts attention, rotating domain names, or sending the whole message as an image that content filters cannot read. That response takes you into World 2.

World 2 is defined by the attempt to game the system. Plenty of poor deliverability advice circulates, so many senders choose this path in good faith.

It fails because providers employ skilled, dedicated teams whose job is to spot the workarounds senders use against their filters and shut them down. All gaming methods eventually stop working. Every workaround named above is already well understood, and providers run countermeasures built to catch and penalize each one.

Open rates around 0.1% are typical in this world, and the standard "solution" to poor opens is to send more. Often the aim is no longer the Inbox at all, only the Bulk or Spam folder, as long as the mail is not refused outright.

What makes email wanted and expected

1. Permission is essential. Mail that nobody asked for is unwanted by definition, so recipients must have invited you to write to them.
2. What you send should match what people expect. A subscriber who signed up for a "daily deal" and receives a daily advertisement with no deal in it is getting something other than what they wanted or expected.
3. Volume should be reasonable and expected. Sending five messages a day to people who were never told how often you would write means sending more than they expect, and probably more than they want. Tell subscribers how often to expect mail when they sign up.
4. Permission cannot be hidden. Consent tucked into terms and conditions that nobody reads still produces mail the recipient does not expect. A pre-checked checkbox has the same effect, since some people never notice it.
5. The email must be identifiable. A subscriber signed up for a particular brand. If the messages that arrive do not carry that brand, the subscriber sees mail from a sender they do not recognize and will probably regard it as unwanted and unexpected, however good the sign-up process was.
6. Remove inactive subscribers. Once a subscriber has gone a period of time without opening or clicking, stop mailing them. Someone who has ignored three emails a week for six months has in effect "emotionally unsubscribed". Dropping those addresses raises the share of your list that reads and wants your mail, so your sending as a whole becomes more wanted.

Providers say openly that the purpose of their filters is to catch and block mail that recipients do not want or expect.

Examples of gaming techniques (which do not really work)

1. Using too many IP addresses (IP snowshoeing). The sender spreads its volume thinly across many IP addresses, hoping each one sends too little to draw attention. Providers know the pattern and penalize senders who use more IP addresses than their volume justifies. GreenArrow recommends that each IP address send at least roughly 20,000 messages a day.
2. Using too many domain names (domain snowshoeing). The same trick applied to domains: spammers cycle through "disposable" domain names to shed a bad reputation and conceal who they are.

Hard-core spammers go further, with methods that include taking over other senders' ESP accounts, DKIM replay attacks, sending through botnets and abusing open relays. Some of these are crimes.

Measured against the goal of reaching the Inbox:

• Filters are built specifically to detect IP and domain snowshoeing, so using either one can be enough on its own to move your mail to the Spam folder at many providers.
• At best, snowshoeing gets mail into the Spam folder: some messages that would have been rejected outright are delivered to Spam instead.

The two dimensions

Two dimensions separate the worlds, and each is a scale with many positions between its ends:

• wanted and expected at one end, unwanted and unexpected at the other
• not gaming at one end, gaming the system at the other

Progress means moving toward wanted and expected mail, and toward not gaming.

The catch for a sender already in World 2 is that progress on only one dimension does not improve delivery.

• Mail that becomes wanted and expected but still relies on gaming techniques is filtered for the gaming.
• Mail that stops gaming but is still unwanted and unexpected is filtered for being unwanted. This change can even turn mail that used to reach the Spam folder into mail that is rejected entirely.

The two have to improve together.

Less is more: the economics that run against intuition

Making mail more wanted and expected usually means sending less of it, and sending less can earn more money, because the smaller volume reaches the Inbox. GreenArrow illustrates this with a simplified, hypothetical example:

• Mail in the Spam folder is opened 0.3% of the time, since about 95% of recipients never check Spam.
• Mail in the Inbox is opened 10% of the time, 30× as often.
• Every open is assumed to be equally likely to lead to the action that generates revenue.
• The changes that make the mail wanted and expected cut volume by 5×, and they get it into the Inbox.

Volume is 5 times lower while revenue per email is 30 times higher, so total revenue rises 6×.

Making the changes

Becoming more wanted and expected usually takes a close, thorough look at the whole email program. Let data drive it: change something, then watch what happens to complaint rates and engagement.

Expect several rounds, because improving deliverability is an iterative process. Each campaign adds to your sending history, and that history points to the next improvement. The mailbox providers make the final decision to deliver to the Inbox, file in the Spam folder or reject, and these practices aim to make your mail the kind they choose to put in the Inbox.

Related articles

• Basic IP Allocation
• Foundations of Email Deliverability
• Advanced IP Segmentation and Allocation