In my opinion you shouldn't mail pens filled with ink, but last week I received in the mail a pen still filled with Waterman Blue-Black, it wasn't a big deal so I cleaned the leaks and started writing with it straight away.
Yesterday I finally ran out of ink so I started my cleaning routine (which basically means flushing for with lukewarm water until the water comes out clean) and I was surprised to see some dried ink particles coming out. As I kept cleaning the pen I saw more and bigger flakes of ink and it was pretty disgusting.
Maybe I'm a neat freak but I was highly disappointed, I've never seen that much dirt in a pen, not even in pens found at flea markets. It's just a matter of common sense, a clean pen works better than one filled with muck, there is no point at flossing nibs or lamenting poor flow when bits of ink clog everything.