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From what I've understood by reading message headers and settings in Outlook, mails sent between Outlook on my PC and the Exchange cloud service are encrypted with TLS 1.2. Messages moving within the cloud between domains are also of course secured in the same way.

Is this more or less secure than transferring files to a server through an HTTPS connection? And how about when, let's say, mails go from Exchange to Google's cloud. Do they also transfer over TLS?

marked as duplicate by Steffen Ullrich tls May 29 '18 at 10:38

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  • 1
    "Messages moving within the cloud between domains are also of course secured in the same way." [citation needed] – schroeder May 29 '18 at 10:23
  • support.office.com/en-us/article/… – tosa May 29 '18 at 12:24
  • right, between domains within the Exchange fabric not cloud. That's an important detail. Once you are outside that fabric, there is no assurance. – schroeder May 29 '18 at 12:26

You cannot guarantee that emails sent outside of the control of your email provider are sent encrypted. That's up to the receiving email server.

So, no, there is zero trust that anything you send will be encrypted end-to-end (that's why we have all these end-to-end encrypted IM platforms).

Transfering files to a server over TLS offers far more control and security functions with fewer complications (and fewer parties involved). This should be considered the more secure option than emailing files.

  • Ok, thanks. But I can at least assume that our internal emails between Outlook and the Excange cloud move solely over TLS. – tosa May 29 '18 at 12:24
  • @tosa yes, that link can be assumed to be encrypted – schroeder May 29 '18 at 12:25

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