In my opinion, when I changed the email address in my Blockchain.com account to a new one, no message was sent to the old address.  Apparently, according to their algorithm, you just needed to confirm the new email by tapping the confirmation icon in the incoming letter from Blockchain.com to the new email address.  So that’s probably why you don’t have a warning about changing your email address in your old mailbox.

  But we are all interested in how users contact Blockchain.com support.
  Please write later what you got from them.  Were you able to restore access to your wallet?