[apazzolini]

Fastmail's web UI is incredibly good. I've also been using it for several years on my custom domain and have zero complaints.

The migration process was pretty painless. I did a one time import of my historical mail from gmail and then set up an autoforwarder --> specific fastmail folder that I look at from time to time and either unsubscribe from whatever sent an email there or update the address as appropriate.

[notacoward]

Cosigned. I just leave a tab open, don't need an app except for my phone, and I've never been anything but satisfied with the experience. Since 2011, according to my archives.

[StavrosK]

Agreed. Their UI is the fastest web app I've ever used, bar none.