Comparing Email Service Providers? 3 data points you might not know, yet

How many emails do Email Service Providers (ESPs) like MailChimp, Salesforce (ExactTarget), Oracle (Responsys) and others send? What are the biggest brands using their infrastructure? And do they only send solicited and legally compliant emails? Below you’ll find three data points, which shed some light on these questions.

1. Cisco’s SenderBase:

According to its own statement, Cisco’s SenderBase is the world’s largest Email and Web traffic monitoring network. On, you’ll not only find global spam and email volume trends, but also reputation and volume data for sender networks. The latter one is reported on a log scale with a base of 10; in theory, a volume of 10 equates to 100% of the world’s email volume (10^10/10^10 x 100). Likewise, a volume of 7.5 equates to 0.31% (10^7.5/10^10 x 100).

Now, having both pieces of information ready, the global email volume and the sender’s percentage, one can estimate the daily email volume of a sender.

For example, according to the MailChimp website,

MailChimp sends 17 billion emails a month for more than 10 million customers around the world.

15 billion emails for The Rocket Science Group as reported by SenderBase does not look too bad. SendGrid on the other hand claims it

is now sending over 23 billion emails a month, via the cloud, for over 80,000 active customers.

SenderBase reports about 16 billion emails, which seems a bit off. I know other senders are also vastly underestimated in the table of monthly sending volumes. So these measures are interesting, but should be interpreted with caution:

Tab 1: ESPs – Monthly Email Volume from May 15 ’16 to Jun 13 ’16
Network Mly Volume Avg Magnitude Cluster
sendgrid 15,863,750,660 7.91 (7.5,Inf]
the rocket science group, llc 15,311,360,693 7.89 (7.5,Inf]
exacttarget 13,352,701,144 7.83 (7.5,Inf]
responsys 4,035,832,496 7.31 (7,7.5]
ecircle gmbh 3,830,825,414 7.29 (7,7.5]
silverpop systems 3,307,798,868 7.22 (7,7.5]
epsilon interactive llc 1,010,149,316 6.69 (5,7]
mailjet sas 965,308,333 6.68 (5,7]
optivo gmbh 941,229,706 6.67 (5,7]
emarsys emarketing systems ag 932,770,454 6.67 (5,7]
adobe systems 462,780,732 6.34 (5,7]
selligent sa 55,994,914 5.41 (5,7]
Data from Cisco’s Network

As a side note: What about social networks and their email volumes? Facebook has the lead, that’s no surprise. However it’s interesting to see trends like the weekend downs at LinkedIn, which are ups at Facebook:

Tab 2: Social – Monthly Email Volume from May 16 ’16 to Jun 14 ’16
Network Mly Volume Avg Magnitude
facebook 5,754,351,568 7.46
linkedin corporation 3,639,091,648 7.25
twitter 2,521,947,066 7.11
vkontakte 1,726,144,246 6.94
xing ag 297,639,967 6.13
myspace 48,442,469 5.17
pinterest 30,364 0.94
Data from Cisco’s Network

PS: Note the terms of service on

2. Google’s Transparency Report:

Gmail wants to make email safer for its users. Part of that effort is the Transparency Report for Email encryption in transit. It shows the past and current state of TLS encrypted messages. For example, in the past 30 days, 85% outbound messages from Gmail and 79% inbound messages from other providers to Gmail used TLS encryption.

But there’s more to it than that. The website also offers a query tool for the top domains in terms of email volume to and from Gmail. Using the tool you see how much of the email exchanged with Gmail for any covered domain is encrypted in transit. The underlying dataset is downloadable as a CSV file.

Downloading the data and exploring it further allows you to get a feeling for an ESPs customer base: What are their biggest clients, what geographic regions do they focus on etc. Without going too crazy with additional DNS lookups, the CSV file itself already holds some interesting insights:

Or, in tabular form (20 2nd-level-domains per selected ESPs):

3. Certified Senders Alliance (CSA)

The CSA is an email white list, which is quite popular in the German speaking part of Europe. It is run by the eco Association of the Internet Industry and the DDV (German dialogue marketing association).

CSA senders – most of them beeing ESPs – agree to comply with strict legal and technical quality standards. For example, the CSA is responsible for the wide adoption of DKIM authentication since 2014 (see chart & my blogpost on Among the technology partners are big names like AOL, WEB.DE, Yahoo!, Cisco, Cloudmark and Kaspersky.

Now, the CSA website shows a list of senders that are pilloried due to too many violations of the CSA admission criteria (pdf). It reports the number of reprimands and a possible loss of the white listing status. I already wrote a blog about how CSA reprimands are issued. The reported number of reprimands must of course be seen in proportion to the (unknown) sending volume in Europe; the more emails an ESP sends, the higher tends to be the risk of complaints. However, one might at least question why the number of reprimands skyrockets. The following chart recalls personal notes to the best of my knowledge:

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