How Smart Marketers are Improving Email Deliverability and Avoiding the Spam Box

How Smart Marketers are Improving Email Deliverability and Avoiding the Spam Box
Email Marketing AI Tools

So what if 99% of your emails are getting delivered?

It doesn't mean that even 1% of your audience is actually seeing your emails. 

In fact, it is estimated that one in every six emails never reach the inbox. About 17% of emails go to spam. 

When HubSpot reports that 99% of emails are getting delivered it means that those emails are not bouncing. It does not tell you anything about whether or not your email made it through spam filters. 

We recently sat down with Mike Donnelly, CEO of SeventhSense, the AI-powered email delivery optimization platform for HubSpot & Marketo. We discussed why so many emails go to spam and how marketers can make sure their emails actually land in the inbox. He had a lot to say! You can watch the full conversation here: 


The Fundamental Problem of Email: No Barrier to Entry 


The fundamental problem of email is that there is no barrier to entry. Anyone could sign up for Constant Contact, MailChimp, or HubSpot, pay for a list of email addresses from a list provider like Zoominfo, and start spamming thousands of people within an hour. (Don’t. Do. This!)

Because it's so easy for anyone to do, Google, Microsoft, and other inbox providers are waging war on spam. They are spending billions of dollars a year on AI to separate the wheat from the chaff so that only legitimate emails land in your inbox. 

So how do marketers send emails their audience will actually see? 

Building a Healthy Email Program

First, marketers need to reconsider how they approach their email program compared to their Pay-Per-Click (PPC) efforts. 

Donnelly told us that "PPC is the house you rent while email is the house you own."



PPC = The house you rent.

Most organizations spend tons and tons of money on acquiring leads through PPC advertising on channels like Facebook, YouTube, LinkedIn and Twitter. Advertisers effectively "rent" target audiences from these social media companies. You can advertise to those audiences for as long as you pay for the ads. If you are running effective ads you (hopefully) can collect their email addresses. But are the email addresses you collect from those audiences even qualified?

Most organizations spend the vast majority of their investment dollars, time, and energy into the house they rent. 


Email= The house you own


Email on the other hand is your list. A company's email list is one of the most valuable pieces of intellectual property a company can own. As marketers, you can decide when to reach this audience and how often. 

You should treat your email list with the respect you would show toward a home you own. As responsible homeowners, it's important to keep your email list clean and updated. 

Being a responsible owner of your list also means not abusing it. So often we see companies that think email is free. They think, "We need more leads, we need more activity, we've already paid for HubSpot—Let's just send more emails!"  

But there is a cost– and the true cost is the attention of your recipient. 

We all live in an attention economy. Your audience is hit up all day every day with requests for their attention– from social notifications to text messages to Slack messages to emails. If you want to compete with all of the other things vying for your recipients’ attention, your emails should always add value. 

Email Health Score: A Credit Score for Email

So, you are keeping your list clean and making sure the content in your emails add value. Great job!

But is it working?

HubSpot recently rolled out the Email Health tool to help you monitor your email-sending reputation. The tool provides an email health score which is a weighted average of your open, click-through, hard bounce, unsubscribe, and spam report rates, compared with other HubSpot users.  

Donnelly recommends thinking of your email health score like a credit score:

"The way I like to explain it to executives is, you've got a credit score in your personal life, and that determines how much a bank will lend to you. Are they going to loan you money? Under what circumstances are they going to loan you money? Well, if you just keep borrowing from banks and borrowing from banks in your early twenties, and then in your thirties you decide, 'Hey, I'm gonna go buy a house.' Well, the bank is going to say, 'Well, you don't have a good enough credit score, so we're going to loan you money under terms that are untenable, or we're just not going to loan you any money at all.'

The same thing holds true with your domain reputation. Every inbox provider has a different way of doing it. Google is different from Office365, which is different from the free inbox providers. All of them have their own algorithms.

If you just keep sending lots and lots of emails and people aren't paying attention to them, eventually, Google, Microsoft, corporate filtering systems and other inbox providers are going to start saying, 'Hey, we're just not going to loan your money anymore. Or we're gonna loan you money under terms that are untenable.' Which means, 'Hey, I'm just gonna put you in spam. I'm still gonna deliver your emails, but your emails are all going to spam.'


Late 90s early 2000s - keyword centric.

In the early days of the internet, spam filters were keyword centric meaning that words like FREE or Viagra in the subject line would flag the email as spam. Marketers were told to avoid these types of words that might trigger the spam filtering system. That is not “a thing" anymore as the systems have become much more sophisticated. The algorithms don't care about specific keywords anymore. 


Early -mid-2000s - IP Reputation

As the internet matured, spam filters prioritized a sender's IP reputation. Email senders would check the sender's IP address history to make sure that spam emails had not come from that IP address in the past. While it is still a good idea to make sure you have a positive IP reputation, it is not as important as it once was. 


Late 2000s to Mid- 2010s - Domain Reputation

In 2007 Gmail became the leading email service provider and in 2012, they launched Domain Message Authentication, Reporting, and Conformance—or DMARC. This led to the era of Domain Reputation as the most important piece of the spam filtering puzzle. Spam filters look at the past emails sent from your domain to make sure emails coming from that domain are not spam. It looks at interactions with your emails like open, click-through, and bounce rates to judge if your emails are delivering value to your recipients. 


Today - Sophisticated AI Algorithms

Today's spam filtering systems are extremely sophisticated AI algorithms. The systems now look at the individual email and decide if it will go to the inbox, campaigns folder or spam—based on the content in the email and your recipient's individual email-reading habits. 





Email clients now test emails with a subset of users before deciding whether the email will land in the inbox or in spam. 

For example, let's say you send an email to 1,000 people and each of them have a unique domain. Google will identify a subgroup of people (let's call it 100 users) from within the list of 1,000 emails that are highly-engaged email users. They check their emails regularly, clean up their inboxes and respond to emails quickly.

Google will deliver your email to that sub-group and listen to the engagement that the email gets. It observes positive signals like people opening and clicking on the email, as well as negative signals like people immediately deleting the email or marking it as spam. 

If the majority of the signals are positive, Google will deliver that email to the inboxes to the remaining 900 emails on the list.

If the majority of the signals are negative, the email will go to the spam folder. 



If your company uses an Account-Based Marketing (ABM) Strategy you can still send emails to targeted accounts, you just need to make sure that you are doing so in a way that is mindful of how today's spam filters work.

Here are 4 tips for sending ABM Emails without damaging your domain credibility:


Run Your Emails through an Email Verification Service

The first thing you should always do is run your list of email addresses through an email verification service like Neverbounce or MailFloss

Email Verification software works by pinging the servers of those on your email list and confirming that the ping is accepted by the server. This will help ensure that the people on your list are real people and that they are still at the company you are targeting.  


Use Caution with "Burner Domains"

Another approach is to create an alternative domain or "burner domain" and send your ABM emails from that domain. This can help the sales team reach their cold prospects without inhibiting marketing's ability to nurture inbound leads. You have to be extremely careful with this approach, however, because if your burner domain gets tied to your primary domain you could do permanent damage to your domain authority.

If you are considering using a burner domain, we recommend thinking long and hard about why you need one. If the answer is so you can spam people, you should reconsider your strategy. 


Send ABM Emails Very Slowly 

Don't go out and send 5,000 emails to ABM targets on the first day. That will immediately flag you as a spammer.  

Instead, start with 5 emails, listen to the response, send 10 more the next day, listen to the response, and so on. Never send more than 50-100 emails a day from a burner domain. 


Trickle your Emails to Avoid Rate Limiting Filters

Many corporations implement rate-limiting processes that flag when the same email is sent to many people within their organization at the same time. So if you are running an ABM campaign and you are emailing 25 people at the same account, you want to stagger the emails to those so that those 25 emails get delivered at different times. If they all hit the server at once, they could hit the rate limit and all get marked as spam. 


Using HubSpot's "Don't Send to Unengaged Contacts" Option




If you've sent emails out of HubSpot you've seen the checkbox "Don't send to unengaged contacts."

This checkbox pulls from a property called "sends since last engagement."

We hear from clients all the time asking if they should check that box. 

Our recommendation is to either use it 100% of the time OR create an unengaged contact list that you select in the "Don't send to" drop-down. What you don't want to do is check the box sometimes and not others. 

Donnelly explains it this way:

"The biggest problem with it is, it's a blunt instrument. It's either I'm going to send to that portion of my audience, or I'm not going to send to that portion of my audience. And unless somebody is a marketing unicorn, I have yet to see a company that doesn't use that feature. But then, every once in a while some executive will come and say, 'Well, this is the CEO's message of the year. This email needs to go to everybody.' So we turn it off. Or, 'Hey, it's our end of year push. We need to send this email out to everybody. We're going to uncheck that box.’

 liken that to rolling a rock up the hill. Every time you use that feature you're rolling the rock up the hill with regards to your domain reputation. You're increasing the odds of going to the inbox. But then, as soon as you turn it off, that rock falls all the way back down to the bottom of the hill with regard to your domain reputation.

Unchecking that box after checking it for most of your emails is like a rock rolling back down to the bottom of the hill because when you uncheck it, you send a big blast of negative signal to the internet in the form of bounces, complaints and low engagement."

Instead of using that check box, we recommend implementing a list-cleaning strategy by sunsetting email addresses that are not engaging with your emails and excluding them from your lists.

Changes in the email ecosystem means that marketers need to take special care of their email sending reputation and treat it like the house you own. A healthy respect for your subscriber's attention will go a long way in guiding your email strategy. 

For more tips on optimizing your email campaigns, your email lists or leveraging HubSpot’s AI-powered email writer, contact us. Watch the full HubSpot Hacks recording with Mike Donnelly.

Hadar Kahn

by Hadar Kahn on April 12, 2023