post office standards

here are two links.

one that deal the post offices guidelines about "zoning" on the envelopes and the other deals with the best (ways that the PO prefers) to have a send to address set up on an envelope.

Also, if you're thinking about using a window envelope go the third link they have a good list of different sizes (or you can try western states envelope). For the shipping label, Don suggested we use the height of the envelope and then make it either square or a little longer. If you would like to work with a standard size of labels that come in sheets Avery is probably the best for those measurements. - - hope this helps 

zoning

writing address

envelope sizes