JMAP

Beta: JMAP support is currently in beta. Fastmail is the first provider preset, with generic JMAP configuration and additional provider presets coming soon.

Kurrier supports connecting email accounts using JMAP (JSON Meta Application Protocol), a modern HTTP/JSON-based alternative to traditional IMAP.

JMAP provides a standardized API for synchronizing mailboxes, messages, and account state.

1. Current Support

JMAP support in Kurrier is currently Beta.

At this stage:

• Fastmail is available as the first supported provider preset
• Mailboxes and messages can be synchronized through JMAP
• Email can be sent through JMAP
• JMAP state changes are used for mailbox synchronization
• Generic JMAP server configuration is coming soon
• Additional provider presets will be added over time

The underlying integration uses the standard JMAP protocol, so support is not intended to be Fastmail-specific.

2. Adding a Fastmail Account

In Kurrier, go to:

Dashboard → Providers → JMAP

Click:

Add JMAP Account

Select Fastmail and enter your Fastmail API token.

Kurrier already knows the Fastmail JMAP session endpoint:

https://api.fastmail.com/jmap/session

Your API token is encrypted and stored securely in the Kurrier Vault.

3. Create a Fastmail API Token

Sign in to Fastmail and create an API token with access to your mail.

Copy the token and enter it when adding the account in Kurrier.

Kurrier uses the token to authenticate with Fastmail:

Authorization: Bearer YOUR_API_TOKEN

Your Fastmail password is not stored by Kurrier.

4. How JMAP Works

JMAP starts with a session endpoint.

For Fastmail:

https://api.fastmail.com/jmap/session

Kurrier requests this endpoint to discover:

• Available accounts
• JMAP capabilities
• Mail capabilities
• API endpoint
• Upload and download endpoints
• Account information

A simplified session response looks like:

{
  "apiUrl": "https://api.example.com/jmap/api/",
  "downloadUrl": "https://api.example.com/jmap/download/{accountId}/{blobId}/{name}",
  "uploadUrl": "https://api.example.com/jmap/upload/{accountId}/",
  "accounts": {
    "ACCOUNT_ID": {
      "name": "user@example.com",
      "isPersonal": true
    }
  }
}

Kurrier uses this information to configure the connection automatically.

5. Verification

When a JMAP account is added, Kurrier verifies the connection against the JMAP session endpoint.

Verification checks that:

• Authentication succeeds
• The JMAP session is available
• A usable account can be discovered
• Required mail capabilities are available

Once verification succeeds, the account will appear as Connected in the Providers page.

6. Mail Synchronization

After connecting the account, Kurrier initializes the available mailboxes and begins synchronization.

JMAP exposes structured objects for mailboxes and messages and provides state values that allow Kurrier to retrieve changes since the previous synchronization.

This avoids maintaining a traditional long-running IMAP connection.

7. Updating Your Token

If your Fastmail API token is revoked or replaced, go to:

Dashboard → Providers → JMAP

Find the account and select:

Update Token

Enter the new API token and save it.

8. Generic JMAP Providers

Generic JMAP configuration is coming soon.

This will allow you to provide a JMAP session URL and credentials directly instead of selecting a predefined provider.

Additional JMAP provider presets will also be added as compatibility is tested.

Because Kurrier's implementation uses the standard JMAP protocol, the goal is to support any sufficiently compatible JMAP mail server.

9. Troubleshooting

Authentication failed

Check that your Fastmail API token is valid and has permission to access mail.

If necessary, create a new token and use Update Token in Kurrier.

Account does not connect

Make sure the API token has the required permissions and has not been revoked.

You can try generating a new Fastmail API token and reconnecting the account.

Something doesn't work as expected

JMAP support is currently in Beta.

If you encounter compatibility or synchronization problems, please report them through the Kurrier GitHub repository.

10. JMAP vs SMTP/IMAP

If you're using Fastmail, JMAP is the recommended way to try the new integration.

For other providers, continue using SMTP/IMAP until generic JMAP support or an appropriate provider preset is available.

11. JMAP Standards

JMAP is an open IETF standard.

The primary specifications used for mail are:

• RFC 8620 — JMAP Core
• RFC 8621 — JMAP for Mail

JMAP Core defines sessions, capabilities, requests, responses, and state management.

JMAP Mail defines operations including:

• Mailbox/get
• Mailbox/changes
• Email/get
• Email/query
• Email/changes
• EmailSubmission

Kurrier's JMAP integration is built around these standards rather than a Fastmail-specific mail API.