alt Hacker NewsFastmail provides an easy way to migrate [0]. I setup a label in my Fastmail account that will tag all mail coming in from Gmail. Then you go through that list at your leisure and make the requisite contact with the people or services emailing at the old address. It's really not difficult at all. I've been on Fastmail for ~4 years now, and haven't once considered looking back or regretted it. Good luck.
Exactly this! After ~3 years I rarely receive an email with the Gmail tag now that all contacts/services have been switched over (or unsubscribed). Fastmail is easily my most valued paid service, and yet I never have to think about it. Just works very well.