We did a mail drop just once, the wife sent it out to a designated business on the FT and we picked it up there. No ID needed, I just told them "Hi I am Max Power and I have a package waiting" signed a paper and I was gone.
However I do think you need ID if you're picking up a drop at a post office. There is a website that lists all resupply points on the FT so I am assuming the AT as well. But, you need someone on the other end sending it out at the right time.
Also, most have a phone so they might tell their wife to send a different jacket or socks or whatever.
Looking back on that one mail drop, IIRC the website said that variety was important. You don't want to be consuming the same stuff on the trail because you get sick of it. Did MH get sick of his rations? Haven't thought about that yet but worth some others weighing in.
BBM
This was my experience. You get sick of your food when you're thru hiking. Me? I had 33 different dinner recipes that I set up in advance. I introduced them gradually over the course of the hike, with pick ups every 4 days.
Testimony to food boredom.... A couple who were hiking the AT at the same time as me did some mathematical calculations about their food. They determined that the best weight/calorie/nutrition ratio was a certain combination of gorp. They mixed VATS of it. It would be their primary food. To make a long story short.... within a week or two, very large ziplocs full of gorp were being abandoned in shelters..... LOL It was no time at all before they were sick of the same ol' same ol'.
Another food strategy is to put up with the daily boredom of ramen+tuna, and eat variety when you get to town. On the AT, that could be as often as very 2 days. The AT is not exactly remote.
I also want to make a correction about weight gain.
My observation is that frequently men lose weight when they're thru hikers. In fact, if they start the trail on the stringy-side, they will almost certainly have to abandon the trip because they will get too thin.
Not so women! Often women will GAIN weight. The reason is that the weight gain is muscle, and muscle is heavier than the other options. IIRC I left the trail at 140 lbs and a size 4. I weighed maybe 120 and size 8 when I began.
And, in case you're curious, you don't just gain muscle in your lower body. Almost all thru hikers use trekking poles (it's probably the reason the AT is even possible for as many people as it is). All the women I knew had RIPPED arm and shoulder muscles from swinging those poles for 2000+ miles.
Floating around the thread, I've seen ideas that MH may have picked up some kind of disease that led to cachexia. Consider that almost all thru hikers spend a great deal of time in the shelters (even if they often sleep in a tent). There are mice and other rodents everywhere, droppings, nibble holes. Heck MH could even have had a mouse eat its way into his pack and left some unwelcome bacteria in his food supply.
And then there's the water issue.... some folks just don't care to treat their water; others think they're treating it, but don't have a process that works; others always treat theirs, but can still get sick (e.g. by cross-contaminating filter hoses). IMO MH could have had a water-born illness.