This question is related to this Super User question.

What cipher suites do Mail Clients (Thunderbird, Outlook, ...) support?

I know and appreciate the service of SSLLabs where I can see the browsers' capabilities in regard to cipher suites. But also mail clients negotiate TLS connections when loading content via https (e.g. images in newsletters). But I was not able to plug the correct search terms into Google to see which mail client supports which protocol version and which cipher suites.

1 Answer 1


Thunderbird uses the NSS library like Firefox, so look at the Firefox report for the ciphers. Similar Outlook uses SChannel like IE/Edge so look at these reports. Apart from that you can simply find out what a specific implementation uses by running a packet capture and then look at the cipher suites offered by the client in the first record of the TLS handshake (i.e. ClientHello).

  • Thanks for your answer. According to this site cipher suite support only depends on the Windows version. So is there no difference between the different Outlook versions when they run on the same Windows?
    – HorstKevin
    Dec 20, 2016 at 11:22
  • @HorstKevin: unless Microsoft specifically configured Outlook to not use the default cipher set different version of Outlook on the same OS should show the same ciphers. Dec 20, 2016 at 11:41

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