The Outer Darkness (Q."Etsëmornië") lay beyond the Ilurambar but within Eä so it may be identical with the Inner Void or those starless parts of it outside of Arda.The Outer Seas traveled by Eärendil the Mariner are part of the "Outer Dark" also Sun and Moon travel the outer Dark, yet the outer Dark is sometimes said to lie beyond the Door of Timeless Night and Ungolianth is said to originate from it and Melkor to be banned into it, seemingly confusing both the inner and Outer Voids.
Notes[]
The confusing of the outer darkness with the starless void and the outer void seems to root in Tolkiens changes to the Cosmology.In the original version Arda was a globule drifting in the etherical outer ocean of Vaiya within the Outer Dark. In later Versions Arda more and more became less a globular world but more a planet and later the "realm of Manwe" and the Solar System, creating the necessety for "two voids" one outside of Ambar or Arda, that is Space,the realm of Stars, the other being a place of non-existence outside of Eä, that is nature or the cosmos.