Excuse me resurrecting this thread, but I'm on topic I think:
Am I correct in assuming that simply deleting my current iCloud account on all my Macs (I've three), and then creating a new account with a different address, is not going to stop Apple's servers from servicing the old address ? In an ideal world, I'd like the old email address to no longer exist at all (I've ended up in a really unfortunate family associated situation which unbelievably is prompting me to seriously consider changing my telephone numbers as well), but in googling around it's beginning to look as though this is not possible ? I'm aware that I can stick a 'holiday' auto response on the old address, but that's not ideal from my pov.
Thanks for any advice.
There appears to be no way of actually terminating an account. This means that messages to that address will pile up in the account until its storage space is filled, and will then be bounced with an 'account over limit' type of message.
You could try setting up forwarding to a completely fictitious address - this should cause a bounce to go to the original sender (test it and see if it does) but of course that will be from fictitious address.
Alternatively you could set up a Rule to move all messages to the account to the Trash, from which they should be deleted after 30 days. That will result in senders getting no response whatever, so it's up to you which result you prefer.