How do all the mailed application materials get sorted...?

<p>As part of my music supplement, my piano and violin teachers wrote recommendations for me. After signing everything, they gave me the letters to mail myself. So all I did was address/stamp the envelopes and slide the letters in before mailing them. But it just occurred to me: was I supposed to put any other identifying information on the outside of the envelopes? Like my name and address and such? Since they were recommendations, I didn’t think I’d have to worry about labeling everything like I had to do with my application materials. But I’ve been thinking…how DO they get everything sorted? I’m worried that my recommendations are going to get lost somewhere. Or are they good at handling this kind of thing? Thanks</p>