Ok, I believe I've heard to send it priority. This true? I know you DO NOT do anything cute, like fed ex, must sign for it packages.
Some agent somewhere recently said she places mail that comes in the hard cover Priority Mail Envelope, which keeps material so neatly in place and pristinely in shape, at the top of her heap each day. Seemed logical to me, as I asked myself, what mail do people tend to look at first? And 50 pages can be fit into the envelope without any difficulty; and, as someone pointed out, for $4.05. So, in addition to protecting the condition of the material,
I get the impact of Express Mail for 1/4 the cost.
Confirmation postcards are familiar to people in publishing, and unlikely to offend most agents or editors, but they run the risk of going astray (under a pile of papers, accidentally/deliberately into the wastebasket, or just plain ignored).