Email Deliverability March 2021 [Infographic]


Oct. 6, 2021

Roberta Phillips

Email Deliverability March 2021

Update: Please find our latest deliverability test results from April 2022 here

For those who were eagerly awaiting this moment, I can announce that our latest deliverability results are finally here! Making this our seventh email deliverability test to date.

Of course, this round wasn’t without surprises. In fact, as you’ll see, there were quite a few movements in the charts.

If you’d like to make a comparison between this test and the previous one, check out our test from September 2020.

For those of you who are coming across our tests for the first time, this is something we started doing back in August 2017 in order to monitor the deliverability rates of the world’s most popular email marketing services.

The number of providers we look at has increased slightly since then; this round we included a total of 15 different email services, three more than the last round. The providers we added are: HubSpot, Omnisend and Moosend.

How do we carry out our tests?

Five separate tests are carried out over the course of five weeks, using the delivery testing tool Glockapps. You can read more about our methodology here, and also see how the tools have performed over the years.

What Exactly is Email Deliverability?

To avoid any confusion, let’s take a look at what email deliverability means before we analyze the results.

Email delivery is when an email is successfully delivered to the receiving server

Email deliverability is when an email successfully arrives in the person’s inbox

Just because your email was delivered, does not mean that it made it to the right place: the reader’s main inbox. There are, in fact, a number of places your email can end up:

  • the spam/junk folder;
  • in the case of Gmail, the Promotions tab;
  • or, worst of all, it goes missing (undelivered)

The term ‘email deliverability’ covers all the above scenarios, and that’s what we’ve been testing.

inbox placement glockapps

Note: In our tests, deliverability was calculated based on the percentage of emails that successfully reached recipients’ mailboxes – regardless of whether they landed in the main inbox or a secondary tab (e.g. Gmail Promotions). If you’re interested in the breakdown between Gmail’s main inbox and the Promotions tab, we cover this in the second table.

So, without further delay, let’s dive into the results of our latest email deliverability test!

email deliverability march 2021

Email Deliverability Rankings: Takeaways

  • Mailerlite, a previous deliverability champ, managed to win back its title with an impressive score of 97%! This is the highest any of the providers have been able to achieve in the time we’ve been testing their deliverability (four years!)
  • ConvertKit, our winner last round, got pushed off the top spot, but it didn’t do too badly with 96%, 1% higher than last round
  • Sendinblue, a past winner, has shot back up the charts with 96%
  • ActiveCampaign, who saw a real drop in deliverability last round, has swung it back around with 91%
  • HubSpot, a new addition to the tests, scored an impressive 92%
  • Yet again, GetResponse was the only provider not to land a single email in Gmail’s main inbox (100% landed in the Promotions folder)
  • Benchmark continues to see an improvement in results, yet it still only has a deliverability rate of 75%, which is well below the average
  • Overall, the average deliverability has gone up again (88.9%). In fact, it’s the highest it’s been since we started testing in 2017. We’re very pleased to see that email marketing services are clearly investing more resources in this area

Where Did The Emails End up?

The table below shows the averages for where emails ended up for each provider: the main inbox, another tab, the spam folder, or if they went missing.

Constant Contact82.
  • The providers least likely to have emails end up in the spam folder were Sendinblue (1.5%), Drip (1.5%) and MailerLite (2.1%)
  • The providers most likely to be flagged as spam were Benchmark (22.7%), AWeber (17.9%) and Mailchimp (12.9%)
  • The providers least likely to have emails go missing were Mailchimp (0.1%) and Moosend (0.7%)
  • The providers most likely to have emails go missing were Drip (10.7%) and Omnisend (6.2%). Benchmark usually has a high percentage go undelivered, however, this round saw that number decrease by 86%

Deliverability to Most Popular Mailbox Providers

There are heaps of mailbox providers out there, and while our tests were sent to over 30 different ISPs internationally, we couldn’t record them all. Instead, they were weighted according to importance. The following table summarizes the average deliverability rates to Gmail, Yahoo, Microsoft (Hotmail + Outlook) and AOL. For Gmail, we’ve differentiated between the emails that arrived in the main inbox and the Promotions tab.

Constant Contact60%40.00%100%100%100.00%


  • The providers most likely to end up in Gmail’s main inbox were Sendinblue (80%), Moosend (60%), ActiveCampaign (60%), Constant Contact (60%), Omnisend (60%) and Drip (60%)
  • The providers most likely to end up in Gmail’s Promotions tab were GetResponse (100%), MailerLite (80%), HubSpot (80%) and Benchmark (80%)
  • Sendinblue, Constant Contact, ActiveCampaign, MailerLite and Drip were able to reach Outlook and Hotmail inboxes 100% of the time
  • Benchmark only managed to reach Yahoo and AOL inboxes 40% of the time and AWeber saw 8% of emails go missing when trying to send to Gmail addresses

Overall Ratings Based on Historical Performance

We’ve seen that deliverability rates tend to fluctuate over time. Just because a tool hasn’t performed quite so well this round, doesn’t mean it doesn't have a good deliverability track record. We’ve assigned a star rating to each provider based on its overall performance over the last 3 rounds of testing. You can also see whether it has performed better or worse compared to the last round.

Mailjet4.5 stars
HubSpot4.5 starsn/a
Constant Contact4.5 stars
ConvertKit3.5 stars
AWeber3.5 stars
GetResponse3.5 stars

With 97%, MailerLite takes our number one spot, as well as our ‘Best deliverability’ award.

best deliverability

With 90.9%, Mailjet wins our ‘Best of 5’ award for best deliverability over the last five rounds of testing.

best of 5 deliverability

How Does This Affect my Email Marketing Strategy?

When you’re choosing a provider, make sure that it has good delivery rates – we’d recommend referring to our historical data to see the upward or downward trends of each tool. You can also do your own tests with Glockapps – here is a sample report.

Email Deliverability Test: Conclusion

That’s another completed deliverability test! I said it was full of surprises, didn’t I?

It’s good to see that the providers are taking deliverability very seriously, and that most tools have seen an improvement this round. Of course, this has contributed to the overall average being so much better than last round.

I hope that you’ve found this deliverability study to be useful, and that it can serve as a guide when deciding on which provider to go with. However, I recommend that you use it as a reference alongside your own research and make sure to carry out your own tests.

If you’re using a tool that’s at the bottom of the table and whose performance is declining (GetResponse and AWeber) it might be time to reconsider. I’d advise you to take a look at your reports and conduct a few tests of your own using Glockapps or another service.

The most consistent providers are Mailjet, MailerLite, ActiveCampaign and Constant Contact.

If you’re currently looking for a new tool, these are good ones to consider. Make the most of free plans and trial periods to run your own tests.

We run these tests bi-annually so keep an eye out for the results of our next round late 2021. Personally, I’m very intrigued to see if MailerLite will be able to keep hold of the number one spot!


Noticed any deliverability issues with your email marketing service? Or have any questions about our tests? Let us know in the comments below!