Email Deliverability Basics: Keeping Your Email Away from the SPAM Box

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“Deliverability” is the measure, usually expressed as a percentage, of how many emails actually make it into the inbox. To create deliverable email campaigns, you must first understand the landscape and the challenges that must be overcome to place a message in an individual’s inbox. Because each receiving Internet Service Provider (ISP), business email exchange, and individual account uses significantly different rules, there’s quite a bit to learn, and the landscape changes every day.

If you’re relying on email marketing to communicate with your prospects, you already know that you’re in for a fierce competition to get your emails read. In fact, according to the Radicati Group, the total number of worldwide email accounts is expected to increase to over 4.3 billion accounts by year-end 2016. But before you worry about getting your emails being read, you must make sure that they’re arriving in the right place, and not trapped in SPAM filters.

Do you know what your current deliverability rates are? If not, don’t worry — if you work with an email service provider or a marketing automation service provider, they should be able to provide them to you.

The Basics of Email Deliverability Rates

Email sent

This is how many messages were in the queue before any delivery attempts were made, but after internal suppression has been performed.

Email delivered

This metric describes how many emails were completely transferred to the intended recipient’s mailbox provider without generating a “bounce” or other delivery error. There are two levels of delivery:

• If the recipient’s email provider rejects the email message, it does not count as delivered. However, if the provider accepts the message, it counts as delivered.

• Once the email message gets past the provider’s filters, it must still make it past the recipient’s own filters. If the recipient has content-based filters set up that prevent the email from reaching the inbox (e.g., being diverted to the junk folder), it generally will count as delivered.

• This is the metric used to purchase email advertising by CPM or third party list rental. You will see it as a whole number and also as an “Email Delivery Rate” percentage (e.g. “95%”).

Email inbox delivered

This metric is an estimation of how many of the Sent emails actually ended up in the inbox. You’ll see it as a whole number or as a percentage (e.g. “90%”).


Bounces are emails that cannot be delivered to the mailbox provider, and are returned to the service provider that sent them. “Hard” bounces are the failed delivery of email due to a permanent reason, such as a non-existent address. “Soft” bounces are the failed delivery of email due to a temporary issue such as a full inbox or an unavailable ISP server.

Email unsubscribe requests

This tallies how many people took an action (such as clicking an “unsubscribe me from this list” link) to unsubscribe from a list.


This tallies how many people clicked a spam or junk button link in their email client to report an email as spam or junk. Other common email metrics, such as opens and click-throughs, are also important, as ISPs look at engagement measures to help determine overall how “wanted” an email is.


List Management is Key to Email Deliverability

Few things affect your email deliverability more than maintaining clean and accurate email lists of engaged subscribers. Even the best lists need constant maintenance. Between the continual turnover of email addresses, loss of interest, and other factors, your email list starts getting stale just as soon as you create it. The staler a list gets, the fewer opens, click-throughs, and purchases it generates. This threatens your engagement and potentially your reputation scores as a sender. Follow good list management protocols to keep your engagement high and your reputation for integrity intact.

Best Practices

• Send only to people who want and expect your email; contacts who opt in are your best prospects

• Confirm or double-confirm subscribers who opt in, when possible

• Encourage recipients to add you to their address books, and make it easy to do so

• Have a clear privacy policy for subscribers

• Grow lists organically; never buy them

• Develop online forms that encourage people to indicate their interests; use this data to create targeted subscription lists

• Make it easy and obvious for contacts to opt out

• Honor “unsubscribe” requests immediately – it’s the law

• Determine an optimal mailing time and frequency, and stick to it, for consistency

• Clean your lists regularly

Keep your lists clean and current through purging and re-engaging. Purging your lists can be a difficult exercise, because no one wants to lose potential customers. Yet your online reputation depends on maintaining a clean, healthy email list. But, be mindful — how you implement purging your email list is just as important as deciding what to purge.

The two best options for purging are:

1. Simply remove any addresses that meet purging criteria (usually length of time and lack of activity)

2. Send a re-engagement email asking users to take an action to stay on the list

You should plan to purge any address displaying no activity for 12 months. But the timeframe that works for you depends on the typical buying cycle, engagement, and conversion metrics for your specific products or services.

Too often companies don’t think about purging data until significant email delivery problems have surfaced. If you wait until your email is blacklisted or delivered to the junk folder, you risk having to make much more aggressive purging decisions than marketers who proactively manage their data.


Sending a re-engagement message offers a chance to win back the recipient. A re-engagement message usually alerts a recipient that their subscription is expiring due to lack of activity, and entices the user to opt in again to continue receiving the email. Re-engagement messages provide the benefit of shedding abandoned accounts or spam traps from your list. Your list will lose some numbers, but usually the people lost were unengaged, poor prospects anyway.

For very valuable lists, marketers may use a series of emails enticing the recipient to come back. This can have a better response rate than a single email. If a subscriber doesn’t interact with the re-engagement email, then it’s time to remove their address from future sends. Consider the 1-10-100 rule. According to SiriusDecisions: “It takes $1 to verify a record as it’s entered, $10 to cleanse and de-dupe it, and $100 if nothing is done, as the ramifications of the mistakes are felt over and over again.”


Best Practices for List Cleaning and Maintenance

• Clean your lists on a regular basis. We recommend that you perform a cleansing quarterly, at a minimum

• Remove distribution, role-based, or administrative addresses such as “” or “”

• Monitor feedback loops so you can identify and immediately remove people who complain

• Understand the engagement cycles of your sales process

• Identify the point where recipient engagement drops; segment disengaged subscribers by useful criteria, such as whether they ever made a purchase

• Re-engage inactive contacts with messaging and offers targeted to their specific segment

• Purge inactive, unengaged contacts when necessary

In Conclusion

While understanding the basics of deliverability and list management is important, don’t lose sight of the fact that it’s really all about the content that you’re sending. Focusing on quality, stand-out content will make a huge impact on your deliverability rates.  Truly excellent content aligns with your company’s brand strategy, presents a clearly actionable opportunity to the reader, and delights your customer. Implementing some of the above basic email deliverability fundamentals and activating an engaging content strategy can enhance your sender reputation, and help you stay out of the SPAM box.

Need expert support on email deliverability or engaging content? Check out our helpful whitepaper ‘Best Practices for an Email Marketing Strategy’, our email marketing services or contact us for a casual chat about your email pain points and objectives.


Interested in more?

Best Practices in Email Deliverability

Best Practices For An Email Marketing Strategy


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