... such as forwarding to addressee relocation, then I can understand an additional charge (postage due) when the USPS has to do something additional other than the point-to-point delivery. Then, perhaps, additional postage may be due, but to require postage due because of weight/size or whatever after the clerk affixes metered postage would seem strange...

If there is a site that makes it all clear, please let us know.

JB