If you are going on Leave or TAD for more than 5 consecutive days, you required to notify the Post Office and leave specific written mail disposition instructions on a 
DD Form 2258 prior to your departure. During this temporary absence, you can authorize your neighbor or trusted friend to come by and pick up your mail for you (although this is not a requirement). This would be a great help to us and more convenient for you. (Don’t forget to give them your PO Box key!). For your protection, only you or your command-sponsored spouse may provide us with mail disposition instructions and it MUST be done in person.
If you are going on Leave or TAD for over 30 days your mail can be forwarded to your Leave or TAD address (domestic address only). You are required to notify the Post Office and leave specific written mail disposition instructions on a DD Form 2258 prior to your departure. A complete forwarding address is required.
Prior to departing you should send out written change of address notifications to all your personal correspondents including all banks, magazine publishers, and creditors. Additionally, you are required to check out with the Post Office, so that your mail may be forwarded to you after your departure. Be sure to designate the effective forwarding date on your change of address request.
Please note that Pre-sort Standard (Bulk-Rate), Standard Mail and non-profit organization and mailings (most catalogs, circulars, and similar items) will not normally be forwarded to your new address; therefore, if you desire to continue to receive these mailings after you PCS, you must file an address change notification with each of these companies individually.
Remember to always make your address change notifications in writing and notify all correspondents of the importance of using the proper address content and format (including a 9-digit ZIP Code) on all your mail.