Not on the outside if you wrap them and put them in another box that would be fine.
No... It cannot be sent through USPS to P.O. Boxes.
6-10 days depending how you mailed it.
no its returned to your address or just stays at the post office
1 to 14 days or more
The standard is a cancellation showing the city of mailing and the date. Some will include slogans in the bars. There are some that are made to simply cancel stamps and are called Killer Bars.
The post office has the option of returning the letter to sender, if there is insufficient postage.
1 to 14 days or more
Next morning.
3.5 inches by 5 inches I mailed one out and it seemed to work. Anything smaller will be kept by the post office or returned to sender.
3-5 days
1 to 14 days or more
first class 3 to 5 days