If only mature seeds of these species are available, these should always be stored in the refrigerator, and be sown as soon as possible. If necessary store these capsules in paper bags in the refrigerator and send as soon as possible. For long term storage orchid seeds can be stored frozen in airtight glass vials. Pollen are best stored frozen after short drying in small glass or plastic tubes like cryotubes or Eppendorf tubes without hygroscopic agents. The methods described here are very practical, but I do not intend to say there are no alternatives.
Some people use plastic or glass containers, even gelatine capsules to send seeds.
If you have a method that works without problems stay with it. If seed samples are very small don't use plastic tubes, seeds stick to it due to electrostatic efects. Seedlings or tissues from in vitro cultures can easily be sent with a low amount of liquid or solid medium in sterile plastic tubes, in autoclaved glas vials with airtight srew caps, or in autoclavable polypropylene tubes like Falcon or Greiner blue cap tubes. Petri dishes with soft agar and vented dishes cant be sent.