Got into a fight and need advise now?

So me and my BF got into a fight cause we live in a apartment and only have 1 key to the mail box. He's the type that losses everything. He's lost his house key more then 5 times and we've been there less then a year. So now that he's started ordering stuff on ebay he now wants the mail box key so he can check the mail once he gets home. i check the mail once i get off work at 3am and he gets off at 5pm. So he's saying he has to wait an extra day to get his mail. The thing is he pays all the rent and i pay all the utilites. So now his argument is that since he pays the rent he should get the key. I dont want to take the chance that he'll loss the key then we'll have to go to the post office pay to get a new key and then have to wait to get the key. I dont want to take the chance of missing a bill...am i wrong. i told him if he wants a key he can go and get one from the post office. I know its a petty fight but he just pissed me off with this!!!

Why can't you just put the key on a keyrack by the front door and neither of you take it. All my keys hang there. I never lose my keys this way.

Why don't you have him to wear one of those key chains to go around his neck or something. Five times in less than a year is terrible.

instead of him going to the post office and getting another one you could just make sure you keep the key until the other is made it,s simple and you can go on loving instead of fighting