833 Tail housing leaking through bolt hole for Rear Mount?

Maybe it's just the angle of the pic, but it sure looks cross-threaded to me.
Those holes are blind, so if you truly do have fluid dripping from that hole, it may be a cracked housing- possibly due to the bolt being forced in there cockeyed.
I would do my best to get that bolt out of there, and then see if that is really the source of your drip. I doubt it, but you never know. At least that will give you the opportunity to chase the threads and get a new proper bolt in there while you chase down the actual leak.
Other possible sources: output seal, speedometer pinion seals, overfilled and coming out the breather, among others.