States of permissibility or rulings in (Sunni) Islam fall under 5 categories (7 for Hanafis). One of those states is _haram_ (impermissible) and the rest are at varying levels of permissibility (_halal_):

 1. Obligatory (_fard_ or _wajib_)
 2. Recommended (_mandub_ or _mustahabb_)
 3. Neither recommended nor disliked (_mubah_)
 4. Disliked (_makruh_)

All the above categories are "_halal_."

To answer your question, yes, if it is not _halal_ then it must be _haram_. There is no "in-between." Imam an-Nawawi's hadith about doubtful matters refers to things about whose ruling we are unsure of (due to a lack of a clear cut text about them or for some other reason); it does not mean that there is a separate category "doubtful" that they fall under.