From what I've read, it's not a very flammable type of oil so it shouldn't be considered hazardous. You just want to make sure it doesn't leak. When I ship anything that could leak, I usually secure the top with a piece of packaging tape, put it in a ziplock and wrap that in some bubble wrap with more tape. Then put that in your box with enough wadded paper or bubble wrap around it to prevent it from being jostled too much. I would not use a padded mailer by itself. If I had something that was very expensive, I might try to find an empty tin and put it inside there to make sure it wouldn't break.
