I find both Apple Mail and iOS Mail very pleasing to the eye but when it comes to search I have a terrible find emails.
That’s why I use Gmail on the web on the laptop and Gmail app on my iPhone.
Every once in a while i go back to native Mail apps and as soon as I can’t find an email I jump ship back to Gmail. Happens all the time.
Could be Gmail not playing nice with other third party apps like Mail or it could be search on native Mail sucks.
I have only have a Gmail account so I can’t speak for Fastmail or Outlook Mail.