Moderation & Safety

Moderation & Safety

Courier includes rate limiting, player blocking, and input sanitization out of the box. Most of it works automatically — zero configuration required.

---

Rate Limiting

Three tiers of rate limiting prevent mail spam. Each tracks sends independently per player:

File: config/courier/config.conf

mail {
  minuteLimit = 5
  hourlyLimit = 30
  dailyLimit = 100
}

Tier	Default	What It Does
Per-minute	5	Max messages a player can send per minute
Per-hour	30	Max messages a player can send per hour
Per-day	100	Max messages a player can send per day

Limits are per-player and shared across servers in multi-server setups. No bypassing them by server-hopping.

Tune to Your Player Count

The defaults work well for mid-size servers. Running a large server with active trading? Raise the minute and hourly limits. Smaller, more casual server? Lower them.

---

Cooldown Permissions

Cooldowns add a delay between consecutive sends. The player’s permissions determine their tier — the most permissive match wins:

Permission	Cooldown
courier.cooldown.bypass	None
courier.cooldown.vip	5 seconds
courier.cooldown.premium	2 seconds
(none)	10 seconds (default)

Cooldowns are separate from rate limits. A player can be within their rate limit but still need to wait for the cooldown timer. Both checks must pass.

---

Player Blocking

Players can block others from sending them mail:

• /mail block <player> — block a player
• /mail unblock <player> — unblock a player

Blocks persist across sessions. When a blocked player tries to send mail, they get an error — the mail is never created or stored.

---

Input Sanitization

Courier sanitizes user input automatically:

• MiniMessage tags are stripped to prevent tag injection in subjects and bodies. Players can’t use formatting tags to impersonate system messages or create misleading content.
• Command placeholders are validated to prevent command injection. Only whitelisted placeholders like {player} and {uuid} are processed.
• Subject length is enforced by the maxSubjectLength config setting, preventing excessively long subjects from breaking the GUI or database.

---

Atomic Package Claims

Every package claim uses a compare-and-set (CAS) operation at the database level. Each package can only be claimed exactly once, even if two requests arrive at the same instant.

No Configuration Needed

Atomic claims are built into Courier’s storage layer. There’s nothing to configure — it just works. This is especially important in cross-server setups where race conditions are more likely.

---

Admin Tools

A handful of admin commands for monitoring and maintenance:

Command	What It Does
/mailadmin debug <player>	Inspect a player’s mailbox data — message counts, statuses
/mailadmin stats	System-wide statistics — total messages, active users, storage usage
/mailadmin cleanup	Force an immediate cleanup of expired mail (normally runs on a schedule)
/mailadmin locker cleanup	Force cleanup of expired package locker entries

---

Next Steps

• Permissions Reference — full list of all Courier permissions including moderation nodes
• Notifications — configure how players hear about new mail
• Configuration — full config.conf reference including all moderation settings