What is JMAP (JSON Meta Application Protocol) & How It Differs from IMAP & POP3

Due to slow email sync, battery drain, and complex setups of IMAP and POP3 protocols, Fastmail introduced JMAP (JSON Meta Application Protocol) in 2014 to provide a faster and simpler way to sync email, contacts, and calendars. That’s why it is important to learn what is JMAP (JSON Meta Application Protocol), and the comparison between JMAP vs IMAP vs POP3.

Today, I’ll walk you through:

• What is JMAP (JSON Meta Application Protocol)?
• Why Was JMAP Created?
• JMAP Standards (As of 2025)
• How JMAP Works?
• JMAP vs IMAP vs POP3 – Quick Comparison
• Adoption in the Real World
• JMAP Security & Authentication
• The Road Ahead: Calendars & Contacts
• How to Use JMAP?
• Author’s Verdict
• People Also Ask

What is JMAP (JSON Meta Application Protocol)?

JMAP is an open IETF standard created by Fastmail to simplify how clients interact with servers. It was later adopted and standardised by the IETF in 2019 (RFC 8620 & RFC 8621). This is a modern alternative to IMAP and POP3. Instead of juggling multiple ageing protocols:

• IMAP for mail retrieval
• SMTP for sending, CalDAV/CardDAV for calendars and contacts

JMAP unifies them into a single JSON-based API that runs over HTTP and WebSocket. 

Example

Imagine you use Gmail on your phone:

• With IMAP, your app constantly checks if new mail has arrived, which wastes battery and data. Additionally, users found that Apple Mail not syncing with Gmail issue via IMAP.
  
• With JMAP, the server just tells your app when something new arrives, which reduces battery draining and data usage. 

Now, I guarantee that what is JMAP is clear to everyone. Next, I’ll explain why it was created.

Why Was JMAP Created?

Working with IMAP, POP3 and SMTP, users face several issues, such as:

• IMAP is chatty and inefficient.
• IMAP, SMTP and POP3 all drain the device battery and affect bandwidth.
• Separate protocols for mail, contacts, and calendars make complicated integration.

So, JMAP was specially designed to solve these issues. It offers:

• JSON instead of legacy text formats
• Unified API for email, contacts, calendars
• State-based syncing (only changes are sent)
• Built-in push notifications via WebSockets
• Simple batching and back-references. This means multiple requests in one round trip.

What is JMAP Standards – As of 2025

Here’s where JMAP stands today:

• Core Protocol (RFC 8620, 2019) defines the session resource, methods like /get, /set, /query, change tracking, and blobs.
• Mail (RFC 8621, 2019) covers Email, Mailbox, Thread, EmailSubmission, vacation, and MDNs.
• WebSocket Binding (RFC 8887, 2020) enables push notifications.
• MDN Extension (RFC 9007, 2021) handles read receipts.
• S/MIME Verification (RFC 9219, 2022) surfaces signature validation.
• Blob Management (RFC 9404, 2023) manages uploads, downloads, and cleanup.
• Quotas (RFC 9425, 2023) standard quota reporting.
• Sieve Scripts (RFC 9661, 2024) manage filtering rules.
• Contacts (RFC 9610, 2024) uses JSContact as the modern data model.
• Sharing (RFC 9670, 2024) standardised the sharing of mailboxes and objects.
• Calendars (Internet-Draft, 2025, in RFC Editor queue) will pair with JSCalendar.

As we learned what is JMAP standards are. Now, this is the right time to learn how it works in the next section.

How JMAP Works?

JMAP works like a modern web app, fast and reliable, unlike IMAP/POP3, which for slower networks. When I build JMAP systems, these are the ideas I rely on:

1. Session Discovery – One request gives all server details.
2. Method Batching – Send many calls in one request.
3. Change Tracking – Sync only what changed.
4. Blob Separation – Metadata in JSON, files are separate.
5. EmailSubmission – Submit mail, server handles rules.
6. WebSocket Push – Instant updates, no polling.

If you don’t understand these quick points much, then go through the complete working of the JSON Meta Application Protocol:

• Instead of using the old, complicated IMAP or POP3 rules, JMAP uses JSON and HTTP.
• When your email app needs something, like a list of unread messages, it sends a simple JSON request to the server.
• The server replies with a JSON response that’s easy for the app to read and show to you.
• This same process works for email, contacts, calendars, and even tasks, all through one protocol instead of multiple ones.
• Because it works over HTTP, it works well with firewalls, mobile devices, and modern cloud systems.

What is JMAP vs IMAP vs POP3 – Quick Comparison

Here is a quick differentiation between JMAP vs IMAP/SMTP/CalDAV/CardDAV vs POP3:

Feature	IMAP (Internet Message Access Protocol)	JMAP (JSON Meta Application Protocol)	POP3 (Post Office Protocol v3)
Origin	1986 (RFC 1064, later RFC 3501)	2019 (RFC 8620 Core, RFC 8621 Mail, plus extensions)	1988 (RFC 1939)
Primary Purpose	Synchronise email across devices	Synchronise email, contacts, calendars	Download emails to a single device
Transport Protocol	Custom protocol over TCP	Standard HTTP/HTTPS + WebSocket	Custom protocol over TCP
Data Format	Text-based	JSON, widely supported	Text-based
Sync Model	State-based but chatty	Efficient sync with /changes + batching	Simple download/delete
Push Notifications	Limited	Built-in via WebSocket (RFC 8887)	None
Mobile Efficiency	Poor	High	Poor
Multi-Device Support	Yes, but inefficient	Yes, with efficient state tracking	Weak
Scope	Email only	Email, contacts, calendars, filters, quotas, sharing	Email only
Server Requirement	The mail server must support IMAP	The mail server must implement JMAP capabilities	The mail server must support POP3
Common Use Today	Email providers – Gmail, Outlook, Yahoo, etc.	Growing adoption – Fastmail, Thunderbird, Cyrus, Apache James, Stalwart	Rarely used
Best For	Cross-device mail access	Unified syncing of mail + contacts, + calendars	Offline-only email access

Quick overall summary:

• JMAP uses HTTP/WebSocket vs IMAP/SMTP’s custom protocols.
• JSON (developer-friendly) vs verbose text.
• Batched requests vs multiple round trips.
• Built-in vs inconsistent hacks.
• One protocol vs four separate ones

One point is the same: with any protocol, you need JMAP, POP3, SMTP, or IMAP Backup.

Adoption in the Real World

In 2025, JMAP is used by several services, including:

• Fastmail runs it in production.
• Cyrus IMAP has strong JMAP support.
• Apache James supports JMAP for mail and submission.
• Stalwart Mail Server is built with JMAP at its core.
• Thunderbird is rolling out JMAP support, first in Thunderbird for iOS, then on desktop.

One important thing, if you decide to migrate Fastmail to Microsoft 365, then in that case, you can’t use JMAP, as it doesn’t support this protocol.

What is JMAP Security & Authentication

JMAP builds on existing web standards:

• Transport: HTTPS and WSS (WebSockets over TLS).
• Authentication: OAuth 2.0 / OIDC bearer tokens.
• Extensions: Support for S/MIME verification and signed data via dedicated RFCs.

The Road Ahead: Calendars & Contacts

• Contacts are already standardised (RFC 9610) with JSContact as the data format.
• JSCalendar is standardised, and JMAP for Calendars is almost an RFC \

That means by 2026, I expect, it’ll fully replace IMAP, SMTP, CalDAV, and CardDAVJMAP, covering: mail, contacts, and calendars.

How to Use JMAP?

If you were building a new email/contact/collaboration system right now, so let’s:

• Start with JMAP Core + Mail + Contacts.
• Implement WebSocket push for real-time sync.
• Add Sieve, Quotas, and Sharing as needed.
• Plan for JMAP Calendars once the RFC is finalised.

Author’s Verdict

For me, working with JMAP is efficient compared to IMAP/SMTP’s complexity. I believe that in the next few years, JMAP will become the default way clients and servers sync mail, contacts, and calendars. 

That’s why, in this discussion, I explained what is JMAP (JSON Meta Application Protocol), JMAP vs IMAP vs POP3, and related things in detail. 

If you’re a developer, an organisation’s admin, then it is suggested to seriously think about switching to JMAP from other legacy protocols.

People Also Ask

Q. Is JMAP replacing IMAP and SMTP?
Yes, JMAP replace IMAP and SMTP for client-to-server communication. However, SMTP will still exist for server-to-server message transfer.

Q. Which email clients support JMAP?
As of 2025, Fastmail’s web and mobile apps, Thunderbird, including its iOS app.

Q. Which mail servers support JMAP?
JMAP is supported by Cyrus IMAP, Apache James, Stalwart Mail Server, and Fastmail’s infrastructure. 

Q. How secure is JMAP?
JMAP uses HTTPS and WSS (WebSockets over TLS) for transport security. Authentication relies on OAuth 2.0 or OIDC, and extensions like RFC 9219 add support for S/MIME verification.

Q. Does JMAP support push notifications?
Yes, JMAP includes a WebSocket binding (RFC 8887) for real-time push updates.

Q. What data types does JMAP cover?

Currently, JMAP support for Mail (RFC 8621) and Contacts (RFC 9610). Calendars are in the final approval stage.

Q. Do I need to migrate my email account to use JMAP?
No, if your provider supports JMAP, migration is not required. However, if your client doesn’t support it in rare cases, then you have to migrate your data to that client which provides the JMAP option.