When addressing a letter that is intended for the eyes of a specific person, department or agency, "ATTN" should be placed on the first line of the address, followed by the name. An example of a properly addressed first line is "ATTN MARY SMITH."
According to the U.S. Postal Service, any other placement of "ATTN," such as below the city and state or in the corner, is improper. Since automated mail processing machines read addresses from the bottom up, addresses that diverge from the standard format are sometimes misread and delivery is delayed. In addition, the USPS recommends using all-capital letters and no punctuation when addressing envelopes.