Hi
@bowden - diverting DNS is not the same as injecting or adding additional headers to email. On the HH, you can change the dns to use another DNS other then bt.
To be fair, if you run your own mail server, depending upon the mail software, you can strip or add information to the headers. We do this when email passes through our filters, and is used to help with issues or reasons for email been spammed/not sent etc
@weaver - all mail platforms should use TLS 1.2. SSL is deprecated and stopped late last year/earlier this year. Your email client will negotiate the exact encryption to be used, and mail platforms, if setup correctly, should always attempt to use the highest encryption available from the email client
Many thanks
John