[hs86]

MailMate on macOS even though I only use a fraction of its features.

eM Client on on Windows, because is it comparable with Thunderbird in managing my mails but also comes close to Outlook with its calendar and contacts management. Unlike Outlook, it support more open protocols like CalDAV and CardDAV out of the box.

AquaMail on Android, because of its customizability.

I don't use any web clients, because I prefer a unified experience across email providers but from those I tried, I prefer Fastmail's web clients. It somehow feels faster than all these native desktop apps and if I could use it as a generic IMAP/SMTP client like Roundcube, I would use it instead of native desktop apps.