If you’re going to be mailing stuff, why pay for envelopes and boxes when the USPS will send you great ones for free? The USPS will send you Priority Mail flat rate boxes, shoe boxes, envelopes, video boxes, address labels, stickers…. as well as all the various forms you might need… for free.
So, if you sell things on eBay or otherwise do a lot of mailing and have been paying OfficeMax for envelopes and boxes… don’t. Order this stuff, it’s awesome.