When I started "deGoogling" myself a year ago, the first step was to stop using Gmail. When changing my registered e-mail address everywhere on the Internet there was one crucial bit that I completely overlooked: the owner/tech/billing/etc. contact records of a domain that I own. Many registrars send all regular communications to the e-mail address of the user account , not to those in the domain contact records, so…
Worst case you'd raise a ticket (how good is actual support!) and they would be able to change the domain contact information for you because you can already authenticate with the user account that owns the domain.
If this wasn't possible all those domains that have self referencing contact information (eg. abuse@this-same-domain.example) could never be verified.