A friend told me that post office envelopes cannot be reused according to federal law. Is that true?

 I received a book this week in an envelope that says "product of the u.s postal service."  It opened cleanly and is in great shape. It would be a shame not to be able to reuse it.

If the envelope/package is priority mail or express overnight, it can only be re-used for the same class (example - you can re-use a priority mail envelope to send a package priority).  You cannot re-use a priority mail envelope/package to send a PBS book (unless you want to pay for priority).

There are only certain ones you can't reuse unless you pay for that very expensive postage.  I think it's priority, but I could be wrong.  Help me out, people!

edited to add - guess I was typing that as she was!

Yes, you can reuse the regular envelopes that are purchased at the Post Office.

The ones that say "Priority Mail" or "Express Mail" are given away for free by the Post Office, to be used for those classes of mail, and can only be reused for the same class of mail.

That's great news. This is just a regular "cushion envelope" bought at the post office storefront. There are no words indicating Priority or Overnight. The postage is only $2.22 which indicates 1st class. I'll have to let my friend know that she was mistaken and should reuse allowable usps envelopes.  Thanks

Yes Mike, we re-use those all the time.  Postage may vary tho, it will depend on the weight of the contents.

If there is a rate class preprinted on the envelope, it can only be reused for that rate class. If there is no rate class preprinted on the envelope it can be reused for any class of mail.