Just be glad that you have the ability to complain that the postmaster isn’t holding enough crap you didn’t pick up. Most games don’t even give you that much and it’s grab it or lose it. You can collect from postmaster using the app and if you don’t want to go to the tower I would suggest doing that because the game has far more annoying problems than people not doing inventory management consistently. If you scrap during the many many loading screens the game has then you can keep stuff going to postmaster to a minimum. For you to fill up the postmaster as easily as you claim it either means you are missing more than half your engram pickups or you are not dismantling between missions. I can typically play for several hours and come to tower and even on really bad gaps in visiting it’s less than half full. Most legendaries suck right now other than umbrals anyway since everything is getting sunset so for the most part you will just be missing out on some legendary shards.

The postmaster IS your second chance already. Learn to manage your inventory better!!

Your postmaster is your backup inventory though? After every activity you should check it.

Old stuff gets cycled out to make room for new stuff. Just check it every now and then if you’re worried.