TLS on mail servers

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Harry

Member
Oct 13, 2020
19
3
I've noticed something I find interesting and want to share. https://internet.nl is a website that scans for DNS, web, and email security. On the email side, it has a scan for "TLS Version." Every single email service I've scanned for has out of date TLS. It says that the sending and receiving servers have to have matching TLS versions for encryption to work. That makes sense. What I don't understand is why no mail servers have TLS 1.2 enabled. Here are a bunch of examples:


Mail server (MX)Affected TLS versionsStatus
gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt4.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt3.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt2.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt1.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out


Mail server (MX)Affected TLS versionsStatus
outlook-com.olc.protection.outlook.com.TLS 1.1phase out
...TLS 1.0phase out

Even the services that are better about email security come up like this:

Mail server (MX)Affected TLS versionsStatus
mx2.paypalcorp.com.TLS 1.1phase out
...TLS 1.0phase out
mx1.paypalcorp.com.TLS 1.1phase out
...TLS 1.0phase out


Mail server (MX)Affected TLS versionsStatus
mailsec.protonmail.ch.TLS 1.1phase out
...TLS 1.0phase out
mail.protonmail.ch.TLS 1.1phase out
...TLS 1.0phase out


Mail server (MX)Affected TLS versionsStatus
mail.tutanota.de.TLS 1.1phase out
...TLS 1.0phase out


In fact, I haven't found a single domain that says it supports TLS 1.2 or TLS 1.3. Does anyone know why mail servers are limited to outdated TLS? I can understand if they keep old versions for compatibility reasons. I don't understand why they don't support new versions. Also, does anyone know of a domain supporting TLS 1.2 or higher?
 
Are you sure? Running tests on gmail servers using

//email/testTo:

www.checktls.com www.checktls.com
says otherwise.

1611805115239.png
 
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Those test results doesn't list TLS 1.2 because it's not meant for that. The report only mentions the deprecated versions, not all the versions supported by a server.
I did a couple of tests using a tool called sslscan which scans the TLS configuration, here are the results (on some of those host names).
Are our providers perfect? All signs point to no. But they do support TLS 1.2 :)

gmail-smtp-in.l.google.com.
gmail-smtp-in.l.google.com.png


outlook-com.olc.protection.outlook.com.
outlook-com.olc.protection.outlook.com.png

mx1.paypalcorp.com.
mx1.paypalcorp.com.png


mail.tutanota.de.
mail.tutanota.de.png
 
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JulioHM said:
Are you sure? Running tests on gmail servers using

//email/testTo:

www.checktls.com www.checktls.com
says otherwise.

View attachment 284
Click to expand...

Definitely not sure, and now I see what you mean. I was interpreting it as there are only bad versions, but it's only reporting the bad versions. Here is the full explanation:

Verdict:​


At least one of your mail servers supports one or more TLS versions that should be phased out deliberately, because they are known to be fragile and at risk of becoming insufficiently secure.


Technical details:​



Mail server (MX)Affected TLS versionsStatus
gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt4.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt3.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt2.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out
alt1.gmail-smtp-in.l.google.com.TLS 1.1phase out
...TLS 1.0phase out

Test explanation:​


We check if your mail servers (MX) support secure TLS versions only.
A mail server may support more than one TLS version.
Note: Quite some mail servers only support older TLS versions. If the sending and receiving mail server both do not support the same TLS version, they will usually fall back to unencrypted mail transport. Because of that it could be advisable to keep supporting TLS versions with a 'phase out' status for a while. Make an informed decision based on log data on when to disable these 'phase out' TLS versions.
See 'IT Security Guidelines for Transport Layer Security (TLS) v2.0' from NCSC-NL, guideline B1-1 and table 1 (in English).
  • Good: TLS 1.3 and 1.2
  • Phase out: TLS 1.1 and 1.0
  • Insufficient: SSL 3.0, 2.0 and 1.0
Thanks for setting me straight and showing off a tool I'm not familiar with. https://www.checktls.com/TestReceiver
 
EdwinG said:
Those test results doesn't list TLS 1.2 because it's not meant for that. The report only mentions the deprecated versions, not all the versions supported by a server.
I did a couple of tests using a tool called sslscan which scans the TLS configuration, here are the results (on some of those host names).
Are our providers perfect? All signs point to no. But they do support TLS 1.2 :)

gmail-smtp-in.l.google.com.
gmail-smtp-in.l.google.com.png


outlook-com.olc.protection.outlook.com.
outlook-com.olc.protection.outlook.com.png

mx1.paypalcorp.com.
mx1.paypalcorp.com.png


mail.tutanota.de.
mail.tutanota.de.png
Click to expand...

Thanks Edwin!
 
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