JMAP vs IMAP: what the modern protocol gets right
By Reeva Team · May 21, 2026
IMAP has carried email for thirty years. It works — but it was designed for a different era, when you fetched mail from a single desktop and a slow modem. JMAP is the modern alternative: a JSON over HTTPS protocol designed for mobile, multi-device, battery-aware clients.
Here’s what changes.
Efficient sync
IMAP clients poll for changes by walking folders. JMAP clients ask the server what’s new in one request. Less radio time on mobile, less CPU on the server, less time staring at a spinner.
One protocol for mail, contacts and calendars
IMAP only knows about mail. Contacts live in CardDAV, calendars in CalDAV, push needs separate plumbing. JMAP defines mail, contacts, calendars and pushed updates in a single protocol — fewer connections, simpler clients.
Stateful, lightweight requests
A JMAP client sends a batch of operations as one JSON request and gets a single response. No need for dozens of round-trips to mark messages read or move a thread.
Push, the right way
JMAP supports server-sent events and EventSource-style push. New mail shows up the moment it arrives, without battery-burning long polling.
Open and audited
JMAP is published as an IETF standard (RFC 8620 and friends). Any client can implement it. Any server can host it. That’s the same bet Reeva makes everywhere: your data should travel over open protocols you can verify and switch.
What about IMAP?
You don’t have to pick. Reeva speaks JMAP, IMAP and SMTP simultaneously. Use a modern client like the Bulwark webmail or any future JMAP-native app, or stay on Thunderbird, Apple Mail or Outlook over IMAP. Your mail is in the same place either way.