Just wondering, can the network invalidate and throw out a transaction if a) the receiving address does not exist... or b) existed but was modified in say ...the last 30 minutes?
Is there a mechanism to warn the client about this or to redirect(bounce back intact so nothing is lost) the transaction back to the client if the transaction is unsuccessful?
Any info would be appreciated.
Bitcoin addresses have a 32 bit checksum in them. So your chances of an error in the address string producing another valid address is less than one in four billion.
Your client will detect when you enter an invalid address.
All valid addresses "exist" as far as the Bitcoin software is concerned. There is no way to tell that no one holds the private key corresponding to one.
So you can't accidently blackhole your Bitcoins, and there is no need for the transaction invalidation mechanism that you describe.