Good idea, thanks for sharing. So I set up an MX record (on Route 53) to point to Fastmail and also set up DKIM by adding several CNAME records for fm1._domainkey.mydomain.com. FM confirmed pretty quick that those changes were made. The last bit is SPF config. I added a TXT record as per the instructions, but I keep rechecking with FM and it's not verified. Emails from FM currently show up as being sent "via messagingengine.com". Any ideas - do I just need to wait?
Scratch that, seems to be working now. Not showing up as "via messagingengine.com" anymore in spite of the fact that it still hasn't verified SPF. Looking forward to cleaning up my email by switching to FM!
When I decided to switch to FastMail in 2016, I repointed that address at FastMail and the vast majority of stuff moved with me... instantly. FastMail also has tools to import your mail archive using IMAP for what's already in your Gmail account.
Now that all of my mail uses my own domain name, if I ever needed to leave FastMail, it'd be painless... none of my mail is going to a FastMail address to begin with.
My strong recommendation is that people do this even if they intend to stick with Gmail for the time being, just to give themselves the future option.