General
General server settings are grouped on the SystemSettings singleton (found in the WebUI under Settings › Network › Services, Settings › Network › General). This page covers the hostname, the CPU thread pool, and IP address allow / block lists. Per-listener concurrency is described on the Listeners page.
Listeners
Stalwart accepts incoming TCP connections through one or more listeners. Each listener is represented by a NetworkListener object (found in the WebUI under Settings › Network › Listeners), and any number of listeners can coexist on the server.
TLS
3 items
Reverse Proxy
6 items
Auto-banning
Stalwart includes an automatic ban mechanism that monitors incoming connections for abusive patterns and blocks the offending IP address when configured thresholds are exceeded. Once an address is banned, the server drops every subsequent connection from that source, shutting down further abuse without operator intervention.
DNS
3 items
Autoconfig
Autoconfig and autodiscover are discovery protocols that allow mail clients to retrieve server settings from the mail domain without requiring manual configuration. They reduce setup errors and shorten the time needed to add an account to a client. Stalwart implements three such protocols: PACC, the legacy Mozilla Autoconfig, and Microsoft Autodiscover.
ASN and GeoIP
An Autonomous System Number (ASN) identifies the network operator responsible for a range of IP addresses. GeoIP data maps IP addresses to a country, region, or city. Together, these sources describe who operates an address and where it is located, allowing incoming connections to be classified by network and geography.
AI Models
Stalwart can call out to large language models for tasks such as spam classification, threat detection, and message categorization. Any endpoint that exposes an OpenAI-compatible chat or text-completion API is supported, whether hosted by a provider such as OpenAI or Anthropic or run locally through a tool such as LocalAI. This choice lets operators balance cost, latency, and privacy according to the deployment.
Caching
Stalwart keeps a set of in-memory caches in front of slower backends (the data store, the DNS resolver, the authentication subsystem). Caching frequently accessed records reduces latency and takes load off the underlying backends without changing their consistency guarantees.
Enterprise License
Stalwart is distributed as an open-source mail server. Alongside the open-source core, Stalwart Labs publishes a set of Enterprise features aimed at larger deployments that require additional control, security, and manageability. These features target environments that need tools such as multi-tenancy, dashboards, and AI integrations, and are unlocked by an Enterprise subscription.