It certainly can be a bit involved. When I moved from Gmail address to my own personal domain I did it slowly over a few months.
I set my Gmail address to automatically forward to my new email address. Then I setup a quick filter which added a label on everything that had been forwarded. Once a week or so I would look at all the emails that had been forwarded and update them to my new email (or delete them if unwanted).
It certainly can be a bit involved. When I moved from Gmail address to my own personal domain I did it slowly over a few months.
I set my Gmail address to automatically forward to my new email address. Then I setup a quick filter which added a label on everything that had been forwarded. Once a week or so I would look at all the emails that had been forwarded and update them to my new email (or delete them if unwanted).
Did the same thing. Took about a year… Just do one site at a time.