Urgent: NYU application

For recommendation letters

should it be reached before 1 dec.

if i sent by DHL, and the DHL said that they don't have the copy thing.

how the school distinguish whether i can reach the deadline ,

pls advise... thx

"Online applications must be submitted by midnight New York time. All mailed application material must be postmarked by the deadline."  

what does this sentence meant?  

the document reached by 1 dec or just with chop before 1 Dec

the document reached by 1 dec or just with chop before 1 Dec

"Online applications must be submitted by midnight New York time. All mailed application material must be postmarked by the deadline."  

按这句话的理解应该是以邮戳日期为准，因为是postmarked，而不是reach，也就是12月1日之前的邮戳都可以吧。

其它大大怎么理解？