"Report errors to developer" is an optional setting (Settings → Application Settings → Logs) that lets your Mumara Campaigns installation automatically send a report to the Mumara team whenever it runs into an unexpected error, so problems can be investigated and fixed without waiting for a support ticket. New installations are asked during setup (pre-selected, can be unticked); existing installations stay off until you switch it on.
A report contains the error and where it happened, the application version, PHP/database versions, installed addons, cron health, a safe subset of settings and the last few lines of the application log. Only problems in the application itself are reported: failures of the server around it (database, cache or mail server down or refusing connections, a full disk, wrong database credentials) are never sent, because those are for the server administrator. Database queries slower than 5 seconds are reported too, as the statement shape and its duration, never the values. A report never contains your contacts, email content, passwords, API keys or submitted form data; email addresses and IP addresses are masked before anything leaves the server. Reports are queued locally and sent in the background (never during a page load), capped at 5 per hour for the same error and 200 per day (slow queries: 50 per day), and dropped after 3 days if the Mumara error tracker cannot be reached.
The same tab has a Send diagnostic report now button: it sends a snapshot of the installation on demand and shows a report ID you can quote to support. Server administrators can force the feature on/off per installation with MUMARA_ERROR_REPORTING_ENABLED in the .env file, or disable it entirely by setting MUMARA_ERROR_REPORTING_DSN to an empty value.