I have gone over this a hundred times with shipping my coffee. It always comes back to flat rate through the USPS. As much as I hate spending that much, I have found no better way. Its the fastest too.
I dont have to buy boxes or tape. The boxes are always the same size and they are delivered to me as well. I like it just for the ease.
I ship 2x12oz or 1x2lb USPS Flatrate envelope cost $4.75. 3x12oz fit into padded Flatrate envelope $4.95. Next up med flatrate box $10.50, up 8x12oz perfect fit, or 4x2lb 1x5lb etc, then comes lrg flatrate box $14.70. I charge $5 shipping any size order.
I do 12-12oz in a large flat rate box...perfect too.
Good to know, I was wondering how well coffee would ship in those flat rate envelopes. I had even considered shipping to myself to see how well a bag held up.