This feels like an odd post to make because I’m not sure where to start. 😂 I will never claim to be an expert, but I do want to share some of the things I’ve learned.
Winter plant shipping comes with a whole lot of ups and downs. Should I get a heat pack? Should I not? Should I wait to buy until spring? Is insulation enough? Is it too cold this week?
Of course there are risks when shipping plants any time of year, but it’s especially risky during winter.
I have seen lots of photos lately of people trying to ID damage from different sources, so I’m including a couple of photos here to tell the difference.
Generally, cold damage is going to be a floppy, limp plant or leaf. You may have browning after a while, and when shipped, the plants may go from warm to cold to warm and might possibly become slimy. This is caused because water expands when it freezes and the cells in the plant burst. Cold damage can also look similar to oedema (because it IS very similar) and give the leaves a sheer look. (See photos below)
Heat damage (from a heat pack) will look similar to if the plant was sunburnt. Brown or black is common and typically will only be where the plant was touching or closest to the heat pack. In my experience, the leaf may become crispy but it will not show the same symptoms as cold damage. 
(Adding in a side note about heat damage; I’ve received heat damaged plants in the mail before that looked very different from this pictured, but that was due to the foliage being covered in plastic. When plants are shipped with foliage wrapped in plastic, the heat can cause the leaves to melt. I do my best not to have any leaves touching plastic when shipping because it’s so disappointing to receive plant mail when the leaves have melted due to plastic and heat!)
Please note, best practice is to place heat packs near roots but put a barrier between roots and the heat pack so nothing is touching. I would hope you won’t ever see heat damage on a leaf, but if you do, it’s also pictured below.