It is my understanding that the postal rates for first class mail and flat rate priority mail are the same for ALL US addresses - to ALL other US addresses - including Alaska, Hawaii, Guam, and other US protectorates.

Is this correct?

I believe that flat rate is the same to all US Addresses. A first class letter is the same but if you send a small package it can be different depending on the zip code, I think! If it is priority but not flat rate there is a difference. I can remember that some tax returns we sent out ever a different amount for some zip codes, even when they weighed the same. That was for large envelopes that were over 13 oz (but didn't fit in the flat rate envelope)

call your local post office- they will answer postage questions.

As far as I can tell, most shipping (not only mail) is based on weight and distance - and in some cases, bulk/mass is also a factor.

They have a website that can answer all your question.

usps.com

It appears that there is only one phone number to contact:

1-800-275-8777
1-800-ASK-USPS

There are also two levels of Flat Rate Priority. They have a regional rate now. The boxes and postage are only available online. For shorter distances, it is much less than normal priority rates.

this is what i rely on

Same here!

http://reviews.ebay.com/WTH-How-To-U...00000021146713

Some relatively understandable info.