Short: See my last answer - secure is never a black or white decission. The chosen cypher will protect your traffic and its better than plain text.
Long: The client negotiates the supported ciphers with the server and chooses one that fits for him. I *guess* that k9/anroid simply does not support the GCM cipher and therefore uses another one. To get the "best" result you need to list up all supported ciphers of your client and server and choose one, but be warned that if you ask two analyst, you might not get the same answer which is "best" as this dependes on the kind of threats you want to take care of
Oliver
Thanks Oliver.
I had a look at:
https://www.ssllabs.com/ssltest/viewClient.html?name=Android&version=4.4.2
And Android 4.4.2 does support:
ECDHE-ECDSA-AES128-GCM-SHA256
So why then does K9 not connect using GCM? Could K9 mail not support this cipher? If Android supports it does this mean that K9 mail will support it too?
Just trying to figure out WHY I can't get K9 to use GCM!