Email Deliverability Test: A Detailed Look at the Best-Performing Tools

Inka Wibowo

Latest Update: Jan 2023

Email deliverability can really make or break an email marketing campaign. Most marketers know the theory behind boosting email deliverability rates – building and maintaining clean lists, keeping subscribers engaged, developing a good sender reputation, and so on.

But many also know from experience that you can do everything by the book and still have your emails mysteriously disappear after being sent.

Based on our bi-annual email deliverability test, we’ve confirmed what many marketers have long suspected – different email marketing services do have different deliverability rates. And the differences, in some cases, are quite startling.

As a result, we’ve decided to share our results, and have committed to performing regular tests to make sure our results are always up to date. We’ll continue to add them to this page with each round of tests to show you who has got the best email deliverability!

Because we believe email deliverability should be an important factor when deciding on which email tool is right for your business, we’ve also now added this as a criterion to each of our reviews.

Email Marketing Deliverability Comparison: Average Deliverability Rate (Last 3 Rounds)

Over the years, we’ve seen fluctuations in the deliverability of the email service providers (ESPs) we monitor. This table gives you the average scores from our last three email deliverability tests (approximately a year and a half).

Email Marketing ServiceAverage Deliverability Rate (Last 3 Tests)
MailerLite deliverability95.2
CleverReach deliverability93.6
ActiveCampaign deliverability91.7
Constant Contact deliverability90.4
ConvertKit deliverability88.2
Mailchimp deliverability87.9
Moosend deliverability83.9
Mailjet deliverability82.7
GetResponse deliverability82.1
AWeber deliverability78.7
SendinBlue deliverability81.07
Omnisend deliverability75.2
Drip deliverability73.7
Hubspot email deliverability72.1
Benchmark deliverability43.4

Mailchimp’s deliverability might be a surprise to some, considering how popular the tool is. This could even be enough to look for an alternative to Mailchimp. We’d like to see it get scores in the early nineties.

Many people are also very interested in HubSpot’s email deliverability, which, we have to say, was not anywhere near as high as it should be.

You can find the results from all our tests in the table below.

Email Deliverability Test: Results Over Time

These rates represent an average derived from the five email deliverability tests in each testing round.

Provider Aug 2017 % Mar 2018 % Jan 2019 %July 2019 %Feb 2020 %Sept 2020 %Mar 2021 %Oct 2021 %Apr 2022 %Jan 2023 %
Constant Contact89.749390.48889.48991.587.790.992.1
Drip89.1489.8Not tested88.878.88687.981.377.562
MailjetNot testedNot testedNot tested84.894.69489.677.886.184.2
CleverReachNot testedNot testedNot tested79.680.89394.393.396.590.9
HubSpotNot testedNot testedNot testedNot testedNot testedNot tested91.667.168.481.3
MoosendNot testedNot testedNot testedNot testedNot testedNot tested88.788.180.383.7
OmnisendNot testedNot testedNot testedNot testedNot testedNot tested85.185.367.672.5
MailifyNot testedNot tested71.481.6Not testedNot testedNot testedNot tested86.1Not tested
Newsletter2GoNot testedNot testedNot tested83Not testedNot testedNot testedNot testedNot testedNot tested
Overall Average83.7584.7679.6883.8079.685.288.985.384.281

For an analysis of each of the individual test rounds, please follow these blog links:

Email deliverability test July 2017

Deliverability test March 2018

Email deliverability test January 2019

Email deliverability test July 2019

Email deliverability test February 2020

Email deliverability test September 2020

Email deliverability test March 2021

Email deliverability test October 2021

Email deliverability test April 2022

Email deliverability test Jan 2023

As you can see, email deliverability rates can fluctuate over time. Even providers that have done consistently well (ActiveCampaign and MailerLite) have seen surprising results in the past. There are also those that consistently perform pretty badly (Benchmark).

For an analysis of the most recent results, see the blog post (and infographic) from our latest round of email deliverability tests.

The average deliverability for all tools combined was 81% in our latest round of tests. That means 19% of all emails have either gone completely missing or have been caught by popular spam filters. Unfortunately, the average was slightly lower than the last round (84.2%).

This is slightly better than the results achieved through Return Path's research, which found that the average global inbox placement rate was 83%.

Where Exactly Are Emails Landing?

It’s no surprise that there’s a direct correlation between low email deliverability rates, and high rates of email flagged as spam. Below is a breakdown of where exactly emails ended up (whether it was the main inbox, a secondary tab, spam folder, or if the emails went missing), in each test round we’ve completed.

Inbox placement rates August 2017

aug 2017 chart

Inbox placement rates March 2018

march 2018 chart

Inbox placement rates January 2019

jan 2019 chart

Inbox placement rates July 2019

july 2019 chart

Inbox placement rates February 2020

feb 2020 chart

Delivery rates September 2020

sept 2020 chart

Delivery rates March 2021

deliverability chart mar 2021

Delivery rates October 2021

deliverability chart oct 2021

Delivery rates April 2022

delivery rates april 2022

Delivery rates January 2023

jan 2023 email deliverability chart

Based on these results, we can start to see some general trends:

  • Benchmark tends to have a higher proportion of emails get filtered to spam. On the other hand, the same emails sent through ActiveCampaign and Constant Contact were much less likely to be marked as spam
  • Providers are finding it increasingly more difficult to land emails in the main inbox, as more are directed to promotional tabs

Email Deliverability Test: Rates by Internet Service Provider (ISP)

Thanks to the email deliverability testing tool Glockapps.com, we were able to see just how well each newsletter service performed in getting delivered to the four main ISPs – Gmail, Microsoft (Outlook and Hotmail), Yahoo and AOL. Based on our results, you can see that certain ISPs definitely look more favorably upon some tools than on others.

Please keep in mind that Glockapps sometimes adds or removes ISPs/a particular email client to reflect their current popularity on the market.

Deliverability to Gmail

ProviderAug 2017 %Mar 2018 %Jan 2019 %July 2019 %Feb 2020 %Sept 2020 %Mar 2021 %Oct 2021 %Apr 2022 %Jan 2023 %
Constant Contact501001009594100100100100100
Drip100100Not tested86.764100100918586
MailjetNot testedNot testedNot tested959110010097100100
CleverReachNot testedNot testedNot tested8982100100100100100
HubSpotNot testedNot testedNot testedNot testedNot testedNot tested100100100100
MoosendNot testedNot testedNot testedNot testedNot testedNot tested100100100100
OmnisendNot testedNot testedNot testedNot testedNot testedNot tested100100100100
MailifyNot testedNot tested8084Not testedNot testedNot testedNot testedNot testedNot tested
Newsletter2GoNot testedNot testedNot tested95Not testedNot testedNot testedNot testedNot testedNot tested

Deliverability to Microsoft (Outlook and Hotmail)

ProviderAug 2017 %Mar 2018 %Jan 2019 %July 2019 %Feb 2020 %Sept 2020 %Mar 2021 %Oct 2021 %Apr 2022 %Jan 2023 %
Constant Contact84.410010010098.510010094.3100100
Drip0100Not tested10010094.310095.794.30
MailjetNot testedNot testedNot tested43.110010071.476.278.680
CleverReachNot testedNot testedNot tested10063.198.698.695.797.1100
HubSpotNot testedNot testedNot testedNot testedNot testedNot tested94.316.127.195.7
MoosendNot testedNot testedNot testedNot testedNot testedNot tested98.694.280100
OmnisendNot testedNot testedNot testedNot testedNot testedNot tested8092.9020
MailifyNot testedNot tested1675.4Not testedNot testedNot testedNot testedNot testedNot tested
Newsletter2GoNot testedNot testedNot tested100Not testedNot testedNot testedNot testedNot testedNot tested

Deliverability to Yahoo

ProviderAug 2017 %Mar 2018 %Jan 2019 %July 2019 %Feb 2020 %Sept 2020 %Mar 2021 %Oct 2021 %Apr 2022 %Jan 2023 %
Constant Contact100100100100100100100100100100
Drip100100Not tested100100100100100100100
MailjetNot testedNot testedNot tested10010095.682367198
CleverReachNot testedNot testedNot tested10087.597.810010010080
HubSpotNot testedNot testedNot testedNot testedNot testedNot tested98100100100
MoosendNot testedNot testedNot testedNot testedNot testedNot tested100100100100
Omnisend Not testedNot testedNot testedNot testedNot testedNot tested100100100100
MailifyNot testedNot tested8085Not testedNot testedNot testedNot testedNot testedNot tested
Newsletter2GoNot testedNot testedNot tested60Not testedNot testedNot testedNot testedNot testedNot tested

Deliverability to AOL

ProviderAug 2017 %Mar 2018 %Jan 2019 %July 2019 %Feb 2020 %Sept 2020 %Mar 2021 %Oct 2021 %Apr 2022 %Jan 2023 %
Constant Contact92.910010097.1100100100100100100
Drip100100Not tested10085.774.371717171
MailjetNot testedNot testedNot tested1001005794946677
CleverReachNot testedNot testedNot tested17.110094.3100899180
HubSpotNot testedNot testedNot testedNot testedNot testedNot tested83100100100
MoosendNot testedNot testedNot testedNot testedNot testedNot tested10097100100
OmnisendNot testedNot testedNot testedNot testedNot testedNot tested10010010097
MailifyNot testedNot tested74.362.7Not testedNot testedNot testedNot testedNot testedNot tested
Newsletter2GoNot testedNot testedNot tested57.1Not testedNot testedNot testedNot testedNot testedNot tested


What does this mean? Well, if you have a good sense of who your subscribers’ email providers are (in an ideal world for email marketers, that would be Yahoo!), you might consider choosing a newsletter service based on this. Of course, that’s often difficult to know. Plus, as our results show, deliverability to ISPs can change over time.

It’s perhaps more useful to just keep an eye out for any red flags. For example, Microsoft has, in the past, applied more stringent filtering to inbound emails, and some newsletter services – such as Benchmark – still struggle to get through.

Gmail Promotions Tab vs Primary Inbox

While the newsletter services were generally able to deliver to Gmail mailboxes just fine, not all ended up in the Primary tab. Nowadays, even emails that wouldn’t normally be considered ‘promotional’ are ending up in this folder.

Proportion of Gmail-delivered emails that ended up in Promotions tab

Provider Aug 2017 %Mar 2018 %Jan 2019 %July 2019 %Feb 2020 %Sept 2020 %Mar 2021 %Oct 2021 %Apr 2022 %Jan 2023 %
Benchmark2000 (100% went to spam)6.7 (87% went to spam)20 (66% went to spam)74.38083.196.4100
Constant Contact11.4002091.44040606041.5
Drip00Not tested14.720 (36% went to spam)404041.516.140
MailChimp10010060200 (31% went to spam)60606058.541.5
MailjetNot testedNot testedNot tested4042.9606061.56040
CleverReachNot testedNot testedNot tested14.70406078.54012.3
HubSpotNot testedNot testedNot testedNot testedNot testedNot tested8010093.640
MoosendNot testedNot testedNot testedNot testedNot testedNot tested40404038.5
OmnisendNot testedNot testedNot testedNot testedNot testedNot tested40404021.5
MailifyNot testedNot tested4012Not testedNot testedNot testedNot testedNot testedNot tested
Newsletter2GoNot testedNot testedNot tested54.7Not testedNot testedNot testedNot testedNot testedNot tested

Why do my Mailchimp emails go to Promotions?

Many Mailchimp users ask why their emails are going to Promotions. You can see that the rates have fluctuated over the years and that this question was more pertinent between 2017-2019 when 100% were ending up in the Promotions folder. However, nowadays, the percentage of Mailchimp emails ending up in Promotions isn't wildly different from other email marketing providers.

There’s no telling why some providers get sorted to Promotions and others don’t, as Google’s complex sorting algorithm is kept tightly under wraps. Ending up in Promotions is less than ideal, as your email is likely to get lost in the flood of emails that often make their way to that tab. Then again, if your email really is promotional and your subscribers are used to accessing emails from that tab, it may not be a problem. Furthermore, your email would be better off landing here than in the spam folder.

Our email deliverability test methodology

Our tests looked at some of the most widely-used email service providers:

Using Glockapps.com, we ran our first round of testing in August 2017. This round comprised of 5 separate tests conducted over several weeks. We wanted to make sure all conditions were equal, so in each test, we:

  • Set up a sender subdomain for each of the tested tools
  • Authenticated the SPF records and DKIM records where available
  • Used the same email (always text-based, sometimes with links, and sometimes without)
  • Sent to the same seed list of approximately 80 email addresses (representing 28 ISPs worldwide, including Gmail, Outlook, AOL and Yahoo; weighted according to the popularity of the email service)
  • Sent all emails within a half-hour period

Over three thousand emails later, we finally had the results from our first testing round. And we found some pretty big differences in email deliverability rates between providers – ranging from 64 to 92 percent!

Happy with the comprehensive deliverability report we received from Glockapps, we repeated this very same test round in March 2018, and from July 2019 onwards, we included an HTML email as one of our tests. The latest email deliverability test we carried out was in Jan 2023 and we plan to conduct, on average, one every 6 months.

Why do some email marketing platforms perform so much better than others?

We’d love to know what the top performers' secret is – and we’re sure the other tools do too! What we do know is that the ISPs often have the last say on whether an email lands in an inbox. This means that they have to trust the mail server sending that email; in our case, that means the server used by the newsletter service.

If that same server also happens to be sending out emails for other clients that are considered ‘spammy’, the deliverability of your own emails could suffer. Newsletter services, therefore, make it a priority to maintain their server’s reputation. But some are clearly doing a better job of this than others.

Some email marketing services offer customers a dedicated IP address (rather than shared IP addresses), but these come at a high price, and are most likely not affordable for small businesses.

What does this mean for me?

With 50% of B2C users buying through marketing emails once a month, seeing your emails go undelivered could be costing you more than you thought and disrupting your whole email marketing strategy.

When choosing a newsletter service, there are obviously many factors to consider – price, features, usability, and so on. But with these results, we’ve hopefully made it easy for you to shortlist (or discard) a few based on potential email deliverability rates.

Note that we said ‘potential’ – there’s simply no way of knowing for sure how deliverability will play out for each business. Our test results can give you a general idea of what you can expect, and what things to look out for, but your own experience may be very different. If so, we’d certainly like to hear about it!

How to improve email deliverability

In spite of our best efforts to establish the same testing conditions for each tool, it’s true that other factors can play an important role. We have put together a complete guide on email deliverability best practices, where you can find more detailed information on the points below:

Email Authentication

As the sender, you have a responsibility to do your best to increase email deliverability by authenticating emails using SPF, DKIM and DMARC and following best practice guidelines for creating and sending emails. Usually, your newsletter tool will indicate whether all these records have been set up correctly. But you can also test your records with free tools like this SPF checker.

Email Verification

For the sake of their deliverability, no email marketer wants their emails bouncing.

There are tools to validate that an email address exists and can receive emails, which can help to avoid bounces and protect your sender reputation.

However, you can keep on top of list hygiene even without an email checker by unsubscribing inactive emails from your list. Some email marketing tools are stricter than others and will remove inactive emails from your list for you if they bounce a certain number of times.


Try to only send marketing emails people actually want to receive, i.e. only send to fully opted in lists. Sending emails to non-permission-based lists will result in low open rates, high unsubscribe rates, and high spam complaints, all of which indicate an unsuccessful email.

These kinds of results can have a negative effect on sender reputation and will impact future deliverability.


Find the right balance between sending too many and too few marketing emails to your subscribers. Remember that people are bombarded with tons of emails on a daily basis, so, in order to avoid inbox fatigue, only send what’s necessary.

You can even ask them to set the frequency at which they’d like to receive emails from you in their preferences. This can avoid spam complaints.

Monitoring activity

It’s not a good idea to have inactive people on your list as, if you’re sending emails to them regularly, this can affect sender reputation and impact deliverability.

Make sure to regularly check in with the less active people and give them the opportunity to re-engage or opt-out of future emails.

Check out these mass email service providers that help businesses send mass emails via SMTP protocol or API.



27 Jan 2023 – Updated Sendinblue results

24 May 2022 – Added average deliverability of last 3 rounds section