Old iCloud emails linked to Apple ID
When I got my first Macbook in 2009, I had an Apple ID/iCloud and back then you could create multiple email addresses on the same account, all ending in @me.com.
I created quite a few.
Now when I log into the Apple ID, I can see current emails to the main email address (which I have used consistently for the last 11 years), and old email addresses to at least 3 other email addresses I created. Only 1 out of those 3 is still able to receive new emails. I've requested a password reset on a site I haven't been on in years to one of the email addresses I'd completely forgotten about and it hasn't turned up.
So do old email addresses that haven't been used get deleted? Is there something I'm missing? Are multiple email addresses to one Apple ID some long forgotten feature because I can't find any reference to it.
MacBook, 10.11