Support JMAP Protocol as Alternative to IMAP

Feature Request

As a user with a JMAP-enabled mail account (Fastmail, Stalwart, etc.), I want to use Nextcloud Mail
to access my email via JMAP. Currently, only IMAP is supported.

Implementation

JMAP (RFC 8620/8621) support is implemented by:

• Introducing a protocol abstraction layer that allows the service layer to work with both IMAP and JMAP
• Creating JMAP-specific client, mappers, and sync logic under lib/JMAP/ namespace
• Reusing domain models and service layer abstractions across both protocols
• Adding protocol selection to the account setup UI

Key library: SebastianKrupinski/jmap-client-php

References:

• RFC 8620: The JSON Meta Application Protocol (JMAP) - Mail
• RFC 8621: The JSON Meta Application Protocol (JMAP) - Calendars
• https://jmap.io/

Scope

MVP (Phase 1)

• Protocol selection (IMAP / JMAP) in account setup
• Connect to JMAP servers with username/password
• Sync mailbox structure from JMAP servers
• Fetch messages with headers, flags, and IDs
• Flag operations (read/unread, custom flags)
• Move, copy, and delete messages
• Send via SMTP (uses existing flow)
• Use existing threading algorithm with JMAP message IDs
• Integration tests against Stalwart JMAP server in CI
• Existing IMAP accounts continue working

Out of Scope

• Auto-detection of JMAP server capability
• OAuth2 authentication
• Sieve filters
• JMAP collaboration/sharing features

Work Packages

See linked sub-issues.

Follow-ups

• Auto-detect JMAP capability during account discovery
• OAuth2 authentication for JMAP providers
• Sieve filters for JMAP accounts
• JMAP collaboration and sharing features

Dependencies

• SebastianKrupinski/jmap-client-php PHP library
• Stalwart JMAP server docker container in CI

Notes

Implementation note: An AI agent was used in the planning phase of this feature.