I normally use the iOS Mail app to connect to Fastmail. This allows me to use the very useful VIP “inbox” to filter email. But, the Fastmail web interface also

I normally use the iOS Mail app to connect to Fastmail. This allows me to use the very useful VIP “inbox” to filter email. But, the Fastmail web interface also works great in iPhone Safari and provides their search facility. On my Air or Linux workstations, I always use the Fastmail web interface, it’s better than a mail app, unless I’m doing something specialized - then it’s Mutt or even Gnus. You can be logged into Fastmail from several computers simultaneously and processing email. It’s seamless, there is never a conflict. I believe they use Cyrus IMAP.