I've never had a problem with sending or receiving with this setup. FastMail's email servers have plenty of good reputation so they're not blocked.
The only issues I've really had are general custom domain & address choice issues:
Choosing to use me@myfullname.tld was not the best idea. A very tiny number of sites stupidly reject the use of a 2 letter username in the email address. Easily solved by setting up an alias of mail@myfullname.tld though. If I were starting over I would have just made mail@myfullname.tld the main address (and I would have aliased male@myfullname.tld). That also makes it a bit easier for humans to read too. Only 2 letters before the @ blends in too much.
Address hiding that many sites do fails to hide anything. Many times when you log into a site, it will display your email address in a way that's meant to avoid people seeing it over your shoulder. But most sites that do that only hide the username. So I'll see things like m*e@myfullname.tld
The only issues I've really had are general custom domain & address choice issues:
Choosing to use me@myfullname.tld was not the best idea. A very tiny number of sites stupidly reject the use of a 2 letter username in the email address. Easily solved by setting up an alias of mail@myfullname.tld though. If I were starting over I would have just made mail@myfullname.tld the main address (and I would have aliased male@myfullname.tld). That also makes it a bit easier for humans to read too. Only 2 letters before the @ blends in too much.
Address hiding that many sites do fails to hide anything. Many times when you log into a site, it will display your email address in a way that's meant to avoid people seeing it over your shoulder. But most sites that do that only hide the username. So I'll see things like m*e@myfullname.tld