Multi-threading lets Mumara send emails through several parallel worker processes instead of one, dramatically speeding up large campaigns. You configure it under Setup → Multi-threading, which has just two settings: a Status toggle that enables or disables multi-threading system-wide, and Default number of threads to show — the value pre-selected in the threads dropdown when scheduling a campaign. Users can still change that number at scheduling time within their limits.
Thread usage is capped at three levels:
System-wide — a MAX_THREADS value in your .env file limits the entire installation.
Per user — each administrator can be given a "Maximum threads" limit under Setup → Staff Management → Administrators, so individual users can't exceed their allocation.
Per campaign — the value chosen in the scheduling dropdown, bounded by the limits above.
During sending, each thread claims a batch of emails from the queue and delivers them in parallel through your sending nodes, with load distributed across nodes and failed emails returned to the queue for retry.
Worth knowing: more threads consume more CPU, RAM, and connections — a common guideline is about two threads per CPU core (shared hosting: 1-2, small VPS: 2-4, dedicated servers: 8-16+). Start conservative and increase gradually while monitoring server load; a warning appears when you select 10 or more threads. If a user can't pick a higher count, check their per-user limit and the system cap.
