On Tue, 19 Sep 2006 17:10:41 +0000, Bob Eager wrote:
The bar code can be printed as many times as you wish. Use it more than
once and only the first letter to be franked will get through without
postage due charges being raised. Seems a solid solution.

That's an interesting one, though - the idea of "item has been delivered"
must presumably be done at some sort of final sorting office - it says
nothing about whether an item gets lost between final sorting office and
final destination. In other words, it's still not without flaws.