oh crap

Ten to one it'll get through. The reason you have the two mailboxes is so that you can stick stuff in the internal mailbox without a stamp and the USPS won't throw it away. But people mix USPS and internal mail in their mailboxes all the time. It'll get to the university sorting center and diverted to the USPS from there, slightly late but not lost.

Still, I suggest you call up your university's mail center and ask them.

The best bet would be to ask someone in charge of the university mailboxes. They might even be able to get it back for you if need be.

Ahh, ok. I haven't asked anyone in mail services yet, but looking around more it seems like they'll route it eventually. They warn on the website not to, but then there's nothing on the box which suggests that it's not a plain old usps box(except it's red and doesn't have the usps logo). People are just beginning to arrive for next semester anyway, and my guess is I'm not the first yahoo to do this :) Besides, it's not critically important, it's just that if it gets lost it's going to be a hassle for the next few weeks.

I don't think I'll contact them, because they will shut down over the weekend anyway and if I can't go down there until Tuesday next week. I'll just contact the place I was sending to after a week or so and tell them to hold tight, and let me know if it doesn't arrive.

*edit It turns out the box can do outgoing mail if you have an account on file at the mail center, and they put postage on for you, so since mine already had postage it should be ok. Thanks for the help!