A year or two ago I went through every online account I have to change the email address.

I should have kept a record of results. Some were good and easy. Some had no option other than an account closure. Some involved a single contact of support without any real verification that I was actually the account holder. Some involved a protracted string of contact with support that tried to claim I was asking for an impossibility. Some services kept my old email on file and I periodically receive something to my old address.