Overview
Stalwart produces detailed tracing and logging output that can be directed to several destinations in parallel, each with its own severity threshold and event filters. Multiple tracers can be configured side by side; the destination and filter choices determine what each consumer receives.
OpenTelemetry
OpenTelemetry is an open-source standard for distributed tracing and metrics. It defines a common set of APIs, SDKs, and collector services that applications use to emit traces, logs, and metrics to an observability backend.
Log file
Log-file output writes entries to a text file on disk. The file can be rotated at a fixed frequency so that long-running installations do not accumulate a single unbounded log.
Console
The console output writes every log and trace entry to standard error. This is convenient when Stalwart runs in a container environment such as Docker, where the container runtime captures stderr directly.
Journal
The journal is the logging facility provided by the systemd suite, managed by the systemd-journald service. Unlike text-file logging (for example /var/log/syslog or /var/log/messages), the journal captures system and service messages in a binary format, which supports indexed queries and integrity checks.