Where is the attention line placed in a letter?

In the past, it was standard to place the attention line a space below the address of the recipient. However, with the wide use of automated postal sorting machines, placing something in that location can cause mis-sorted mail, delaying the delivery of the letter. A better format is:

Mr. A. Brown, Manager

Purchasing Department

ABC Compay

123 Main Street

Anycity, NY USA

OR

Manager (if you don't know the name)

Purchasing Department

ABC Company

123 Main Street

Anycity, NY USA