You can buy 1.5 ’ x 1.5 ’ x 1.5 ’ cubic boxes at the bookstore for ~ $3, but that’s probably larger than you want. Usually, students kind of do a box exchange. Any box that you receive something in can be left at the Commons Mail Room for other students to reuse. Stop by the mailing office (adjacent to the pick-up counter) to look through their box selection. The used ones are all free. You can also buy boxes/packaging here at the Commons Mailing Office and at the Postal Sub-station in the Games Room of the Union.
Students often receive packages that don’t fit in the mailbox. In this case, you will receive an email to your RPI email address with the subject “PACKAGE RECEIPT NOTICE: ONE EMAIL PER PACKAGE” and you can go pick up the package at the Commons Mail Office during business hours. Check out their website here. The staff is great!