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Jan Schaumann

The top 20 most frequently used mail servers I found are:

01.	10.3 M	mailstore1.secureserver.net.	GoDaddy Hosted Mail
02.	10.3 M	smtp.secureserver.net.
03.	9.6 M	aspmx.l.google.com.	Google
04.	9.5 M	alt1.aspmx.l.google.com.
05.	9.5 M	alt2.aspmx.l.google.com.
06.	6.7 M	alt3.aspmx.l.google.com.
07.	6.7 M	alt4.aspmx.l.google.com.
08.	3.9 M	eforward1.registrar-servers.com.	Namecheap
09.	3.9 M	eforward5.registrar-servers.com.
10.	3.9 M	eforward4.registrar-servers.com.
11.	3.9 M	eforward2.registrar-servers.com.
12.	3.9 M	eforward3.registrar-servers.com.
13.	2.7 M	aspmx2.googlemail.com.	Google2
14.	2.7 M	aspmx3.googlemail.com.
15.	1.1 M	mx3.mail.ovh.net.	OVH / OVH Groupe SAS
16.	804 K	mx01.1and1.com.	IONOS / United Internet AG
17.	802 K	mx00.1and1.com.
18.	793 K	mx4.mail.ovh.net.	OVH / OVH Groupe SAS
19.	784 K	mail.h-email.net.	Unknown / parked domains?3
20.	784 K	smtpin.rzone.de.	Strato AG / United Internet AG
10 comments
Jan Schaumann replied to Jan

Now many domains that include alt1.aspmx.l.google.com. as an MX will likely also include alt2.aspmx.l.google.com., so let's flatten these numbers by MX domain frequency, which breaks down our data set to 21 million unique domains.

The top 20 are:

01.	46.7 M	google.com.	Google
02.	22.5 M	secureserver.net.	GoDaddy Hosted Mail
03.	19.7 M	registrar-servers.com.	Namecheap
04.	7.4 M	outlook.com.	Microsoft
05.	6.9 M	googlemail.com.	Google2
06.	3.4 M	ovh.net.	OVH / OVH Groupe SAS
07.	2.4 M	mailspamprotection.com.	SiteGround
08.	1.8 M	hostedemail.com.	Tucows / OpenSRS
09.	1.7 M	1and1.com.	IONOS / United Internet AG
10.	1.6 M	zoho.com.	Zoho Corporation
11.	1.6 M	jellyfish.systems.	Namecheap
12.	1.3 M	one.com.	One.com
13.	1.3 M	qq.com.	Tencent QQ
14.	1.2 M	ionos.com.	IONOS / United Internet AG
15.	1 M	gandi.net.	Gandi SAS / Your.Online
16.	1 M	rzone.de.	Strato AG / United Internet AG
17.	992 K	kundenserver.de.	IONOS / United Internet AG
18.	973 K	123-reg.co.uk.	123 Reg
19.	835 K	h-email.net	Unknown / parked domains?3
20.	765 K	oxcs.net	EuroDNS / Datacenter Group
Jan Schaumann replied to Jan

We can combine some of the domains by company or parent organization to find that Google takes the lion's share of domains with about 34%, GoDaddy around 14%, Namecheap 13.5%, and Microsoft trailing behind with about 4.7%

A pie chart showing Google (34%), GoDaddy (14%), Namecheap (13.5%), Microsoft (4.7%) and misc other domains
Jan Schaumann replied to Jan

But all that is for _all_ gTLD domains, which includes millions of parked domains, typo-squatting and spam domains, etc.

What if we look at the Top 1M domains?

Let's pull the list from tranco-list.eu/...

Jan Schaumann replied to Jan

For those 1 million domains, we find around 433K distinct MX servers in 230K domains. The top 20 mail server domains there are:

01.	138 K	google.com.	Google
02.	94 K	outlook.com.	Microsoft
03.	59 K	googlemail.com.	Google2
04.	15.8 K	yandex.net.	Yandex LLC
05.	13 K	mimecast.com.	Mimecast Limited
06.	12.8 K	pphosted.com.	Proofpoint, Inc.
07.	9.5 K	qq.com.	Tencent QQ
08.	9.2 K	registrar-servers.com.	Namecheap
09.	8 K	secureserver.net.	GoDaddy Hosted Mail
10.	5.7 K	barracudanetworks.com.	Barracuda Networks
11.	5.5K K	zoho.com.	Zoho Corporation
12.	4.7 K	amazonaws.com.	Amazon Web Services, Inc.
13.	4.4 K	emailsrvr.com.	Rackspace Technology
14.	4.1 K	yandex.ru.	Yandex LLC
15.	3.7 K	iphmx.com.	Cisco IronPort Hosted MX
16.	3.5 K	mail.ru.	VK / Mail.ru Group
17.	3.5 K	ovh.net.	OVH / OVH Groupe SAS
18.	3.4 K	mailspamprotection.com.	SiteGround
19.	3 K	ppe-hosted.com.	Proofpoint, Inc.
20.	3 K	beget.com.	Beget LLC
Jan Schaumann replied to Jan

Google and Microsoft together handle over 60% of the Top 1M domains' mails!

Many other domains use service provides such as Proofpoint, Barracuda Networks, or Cisco / IronPort, but those may of course only sit in front of Google and Microsoft's mail servers as well.

A pie chart showing

Google: 41.1%
Microsoft: 19.6%
Yandex: 4.1%
Proofpoint: 3.3%
Mimecast: 2.7%
Tencent QQ: 2.0%
Namecheap: 1.9%
GoDaddy: 1.6%
Barracuda Networks: 1.2%
Zoho: 1.1%
Amazon AWS: 1.0%
Rackspace: 0.9%
Cisco IronPort Hosted MX: 0.8%
VK / Mail.ru Group: 0.7%
OVH: 0.7%
SiteGround: 0.7%
Beget LLC: 0.6%
Jan Schaumann replied to Jan

So all in all, the answer to the question of who can read your email pretty much boils down to -- yep -- "Google and Microsoft".

Even if your domain doesn't use one of their mail servers, chances are that whoever you are sending mail _to_ does.

Jan Schaumann replied to Jan

Now these companies are probably doing a much better job running and securing your mail than you would, and outsourcing often makes good sense.

But still, this is another example of increasing centralization: our businesses and personal online lives are concentrated in the hands of just a few companies.

Jan Schaumann replied to Jan

Alright, that's all for today. Gotta go and fix my postfix DMARC setup and block a bunch of spammers or something.

And if you don't like social media threads or want to share this outside of Mastodon, here's all of the above in a single blog post:

netmeister.org/blog/mx-diversi

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