I know what you mean... Just this morning I received sunflower seeds from the "Great Sunflower Project" which I`m a part of and the seeds were sent in a regular envelope .. I`d say out of 12 seeds...I got 3. I send all my seeds in a bubble wrap envelope and expect the same in return. Regular envelopes go through a different slot that is not a whole lot bigger than the envelope, only milliters. Bubble wrap envelopes go through a different slot size maybe 1/2 to 3/4 inch. I`m not exactly sure but packing your envelopes properly makes a difference too. It`s contents should lay flat like taping seed packets on a sheet of cardboard so they don`t bunch up at the bottom of the bubble envelope.
I wonder if I`ll get any sprouts from my almost all crushed sunflowers,lol.

Sunnybun, that is very disappointing. I hope some of them will work out for you.

As long as they are not too heavy, most bubble envelopes will fit through the larger sized slot.