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FAQ

These pages answer the questions that administrators ask most often about installing and running Stalwart. Each answer states the fact that resolves most cases and links to the page that describes the mechanism in full. Problems that need a diagnosis, such as mail that is not delivered or a sign-in that fails, are collected by symptom in Troubleshooting.

Most asked

Section titled “Most asked”

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General

Section titled “General”

Is Stalwart ready for production?

Section titled “Is Stalwart ready for production?”

Yes. Version 1.0 is a stable release, and the 1.x series follows rules about what each kind of release may change. Patch releases contain only fixes. Minor releases may add settings or change defaults. Only a major release may change the data format or remove settings.

Even so, back up the data stores and config.json before every minor or major upgrade. A newer release can write data that an older release cannot read, which means that after an upgrade the older release may no longer be able to open the data. See Release types.

Where is my data stored?

Section titled “Where is my data stored?”

Stalwart divides its data among four stores, each suited to one kind of data:

  • The data store holds accounts, mailboxes, message metadata, configuration and other structured records.
  • The blob store holds the raw messages with their attachments and other large objects.
  • The search store holds the full-text index.
  • The in-memory store holds short-lived data such as rate-limit counters.

Only one small file lives on the local disk: config.json. It names the data store and nothing else, because every other setting is a configuration object stored in the data store itself. See Storage and Configuration file.

Is my data safe?

Section titled “Is my data safe?”

Stalwart keeps its data in established database and storage systems, such as RocksDB, PostgreSQL, MySQL, FoundationDB or S3-compatible object storage, chosen separately for each store.

The server does not take backups itself, and two things that may look like backups are not. Copying the files of a running data store is not a backup. The built-in export is an offline dump of a stopped server, intended for moving between backends. Back up each store with the tools of its backend instead. See Backup and restore.

Does Stalwart still use TOML configuration files?

Section titled “Does Stalwart still use TOML configuration files?”

No. Settings are now configuration objects stored in the data store. They are edited in the WebUI, with the command-line interface or through the JMAP management API. The only local file, config.json, says where the data store is and nothing else, because every other setting is stored there. See Configuration.

How many users can one installation handle?

Section titled “How many users can one installation handle?”

No measured figure of users per node is published. A single server grows with its hardware, and beyond that, Stalwart scales out: the data moves to a shared external data store, and a cluster of up to 512 nodes serves it.

For planning, the sizing pages give estimates per connection and per login, labelled as estimates. An IMAP session waiting in IDLE, for example, takes about 70 KB of memory. See Sizing and Sizing memory.

Can messages be encrypted at rest?

Section titled “Can messages be encrypted at rest?”

Yes, per account. A user registers an OpenPGP public key or an S/MIME certificate and enables encryption at rest. From then on, the server encrypts each incoming message with that key before it stores the message.

The matching private key never reaches the server, so only its holder can read the contents of those messages. The encryption covers the contents only: header fields such as the sender, the recipients and the subject remain readable. See Encryption at rest.