Why Mailwell speaks JMAP

What JMAP is and what it changes in Mailwell.

When I moved most of my mail to Fastmail, I wished my mail app supported JMAP. It was one of the reasons I started building Mailwell, so it felt right to explain what it is and why it matters.

What JMAP is

Most mail apps talk to your mail server with IMAP, which dates back to 1986 and has been extended many times since. JMAP is a newer standard for the same job. Fastmail led the work on it, and the IETF published it in 2019. It runs over plain HTTPS, the same way most modern apps talk to their servers.

What it changes in Mailwell

• New mail shows up right away. With IMAP, an app can only watch one folder at a time on each connection. With JMAP, the server tells Mailwell about changes anywhere in your account as they happen.
• Catching up is quick. Mailwell asks what changed since last time and gets just that. Over IMAP, that means checking each folder in turn.
• Aliases show up on their own. JMAP lists the addresses you're allowed to send from, so your Fastmail and Kagi Mail aliases are in the From menu without any setup.
• Sending uses the same connection. There's no separate SMTP server to set up.

What about Gmail and iCloud?

They don't offer JMAP, so Mailwell uses IMAP for them, and Microsoft's own sign-in for Microsoft 365 and Outlook.com. They all end up in the same unified inbox. JMAP is just the better option when your provider has it.

Fastmail and Kagi Mail both support it, and so do self-hosted servers like Stalwart and Cyrus. The docs walk you through setting up Fastmail and Kagi Mail. For anything else, choose Enter settings yourself and pick JMAP.