Installation

Installation

Drop Courier.jar into your mods/ folder alongside Ceremony and Cobblemon. Start the server. That’s it — config files appear automatically in config/courier/.

Requirements

Dependency	Version	Required	Notes
Minecraft	1.21.1	Yes	Fabric only
Fabric Loader	0.17+	Yes
Fabric API	Latest	Yes
Fabric Language Kotlin	Latest	Yes
Cobblemon	1.6+	Yes
Ceremony	4.0+	Yes	Powers storage, GUIs, and cross-server features
Impactor	Latest	No	Required for currency attachments
MongoDB / MariaDB	Any	No	Required for multi-server shared storage
Redis / NATS	Any	No	Required for cross-server mail delivery

Quick Start

1. Download the Courier .jar from your purchase source
2. Drop it into your server’s mods/ folder with all required dependencies
3. Start (or restart) the server
4. Confirm config/courier/ appeared with config.conf, messages.conf, and the guis/ folder
5. Run /mail in-game — you should see the inbox GUI

Done. You’re running Courier.

Start with one server

Get Courier working on a single server before tackling cross-server delivery. The defaults use SQLite and no message bus — zero extra configuration needed.

Single Server

For a single server, there’s nothing to configure. The defaults use:

SQLite : Local file storage, no external database required.

No message bus : Mail stays on the local server. Perfect for most setups.

These are controlled through your Ceremony configuration. Your config/ceremony/config.conf should have:

storageType = SQLITE
messageBus {
    type = NONE
}

If you didn’t touch anything, that’s already what it says.

Multi-Server

Running Courier across multiple servers? You’ll need three things:

1. A shared database so all servers see the same mail
2. A message bus so deliveries propagate instantly
3. A unique server ID per server

Shared Database (MongoDB)

In each server’s config/ceremony/config.conf:

storageType = MONGODB
mongoDb {
    uri = "mongodb://username:password@your-host:27017"
    database = "courier"
}

Note

MariaDB is also supported. See Ceremony’s documentation for MariaDB connection settings.

Message Bus (Redis)

In each server’s config/ceremony/config.conf:

messageBus {
    type = REDIS
    redis {
        host = "your-redis-host"
        port = 6379
    }
}

Unique Server ID

Every server needs a distinct serverId in config/ceremony/config.conf:

serverId = "survival-1"

serverId = "hub"

Caution

If two servers share the same serverId, cross-server mail won’t work. Every server must have a distinct ID.

Verification

After starting your server, check the logs for [Courier] loading messages with no errors. Then test in-game:

/mail

The inbox GUI should open. Now send yourself a test:

/mail send YourName Test "Hello!"

Open your inbox. You should see it. That’s it — Courier’s working.

Troubleshooting

Config files not generating : Make sure all required dependencies are installed. Courier needs Ceremony, Cobblemon, Fabric API, and Fabric Language Kotlin. Check your server log for missing dependency errors.

Database connection errors : Double-check your Ceremony config for correct credentials, host, and port. Make sure your database server is running and accessible from the Minecraft server.

Cross-server mail not arriving : Verify that all servers share the same database, the message bus is configured and reachable on every server, and each server has a unique serverId. Check Ceremony logs for message bus connection status.

Permission errors on commands : Courier commands require appropriate permission levels. Make sure your permissions plugin grants courier.command.mail for players and courier.command.admin for admins.

Next Steps

Ready to send your first mail? Head to Your First Mail — it’ll take about 30 seconds.

Want to customize things first? Check out the Configuration Overview.