Forwarding from Apple iCloud Mail

iCloud Mail forwards with a rule; there's no code to confirm.

Steps

On icloud.com, open Mail → Settings (the gear) → Rules → Add a Rule.
If a message is from — the service's sender address.
Then Forward to — the AlertDesk address with the service's +word (yourname.alerts+servicename@gmail.com). Press Done.
Repeat the rule for each service.

What you should see

The service's next letter on AlertDesk's Feed.

If it doesn't work

The letter shows under Needs a look from your own address: iCloud sent it as you. With the +word AlertDesk still knows the service; or put the sender with the service there.