Even though there is no smartphone with Mozilla's Firefox OS yet, I was still interested to see if the ActiveSync functionality already works. Here is the setup:
The e-mail app is started first
"Other email" is then selected in the mail app
The user information is entered in the following dialog
Autodiscover did not work for me, so I had to make the server settings manually
The value for Account Type must be changed to "ActiveSync"
Unfortunately, after confirming with "Next", you end up back on the page with the "Manually set up account" button. The page only shows a note with "An unknown error occured".
The following message appears in the debug console:
An error occurred during a connection to frankysweb.de:443.
SSL received a record that exceeded the maximum permissible length.
(Error code: ssl_error_rx_record_too_long)
The message indicates problems with the certificate, but the certificate comes from a public CA
Further tests with other certificates (public and self-issued) also failed. Apparently the SSL implementation is the problem here. So I have not yet managed to get Firefox OS and Active Sync to work. So I guess I'll have to wait a little longer 
