I use CiviCRM under Wp 4.4. From civi 4.7 I met the problem in sending mass mails. The sent mail plus bunce number is lees than expected mailings numbers. (I use only Hungarian version). The not sent email is "unknown" state.
Your findigs possible caused my problems, checked only one contact, the settings is "none". If I set it as "Both" and save it, the settings sticks. When I reopen communication references the Email format switch to "none". I don't understand what happens.
Or If I send direct mail to contact, the empty mail arrives.
I tested in http://wpmaster.demo.civicrm.org
with "English" default language, the problem not happens. I tested in my test systems, under Hungarian language settings, the problems is same, in Email format switch to "none" state.