It would help if you let me know the actual mail server you're trying to connect to. You can do it privately to kmansoft / gmail.
Aqua uses EWS (Exchange Web Services) to connect to Exchange and needs Exchange 2007 Serice Pack 1 (released November 2007).
K9 uses the much older "OWA" network protocol, so there is a mismatch right there.
You could actually verify that your server name is correct by trying to open (in a web browser):
https://your_server_name.com/EWS/Exchange.asmxIf it asks you to authenticate (login) then you've got the right server. If you get some sort of "page not available" error, then there is no EWS at that server.