Something feels off about this all in, an under the gun raiser isn't likely to raise with 56,67, or 89, so i would have to think your hand is good at the moment. Could be a pure bluff, he could have a smaller overpair, possibly 88 which gives him an open ended, and would guess that he is probably overplaying his hand, not betting with better cards than yours.

Dang, too long to type it, and now i just look silly saying the same as above.