Renamed user does not receive automated emails

I followed these instruction to rename a user: https://docs.erpnext.com/docs/v12/user/manual/en/setting-up/articles/rename-user

This allowed me to rename the email, but now when someone tags the user in an issue, task etc. no email is sent. Is there something else that has to be done? What is strange is that I am not even seeing the email show up in the queue.

I had this issue also. It looks like the old user name is still cached. You can rebuild by deleting this key from cache with:
frappe.cache().delete_key('users_for_mentions')
from the console. I am not sure why this is not running automatically.