📄️ Overview
This section focuses on the configuration and behavior of outgoing message delivery within Stalwart Mail Server. While inbound pertain to handling SMTP connections received on ports 25 or 465, outbound refers to the outgoing connections initiated to deliver messages to their destinations. These destinations can include remote SMTP servers for messages addressed to external domains or the local message store for delivery to local users.
📄️ Routing
Message routing is the process of determining the final destination host to which an email message should be delivered. This step is essential for ensuring that messages are delivered to their intended recipients accurately and efficiently. In a mail server, routing involves resolving the recipient domain's address to identify the mail server responsible for accepting messages for that domain.
📄️ TLS
Stalwart Mail Server implements TLS support to ensure secure transmission of emails over the internet. TLS (Transport Layer Security) is essential for protecting data in transit, providing encryption, authentication, and integrity to prevent unauthorized access and tampering of email messages. Stalwart Mail Server’s TLS configuration is built on rustls, a modern, high-performance TLS library that prioritizes safety and correctness.
📄️ IP Strategy
An IP strategy determines which type of source and remote IP addresses to use when delivering emails to a remote SMTP server. This configuration allows fine-tuning of both the source IP strategy—which determines the local IP address used when sending emails—and the remote IP strategy, which defines the order in which IPv4 and IPv6 addresses are tried when connecting to remote hosts.
📄️ Limits
Transport limits allow administrators to define constraints and thresholds for email transport and SMTP transactions. These settings provide control over how the server handles message delivery and communication with remote hosts, ensuring efficient use of resources and compliance with organizational policies.
📄️ DNS
The DNS resolver is responsible for resolving human-readable domain names into IP addresses and other type of machine-readable records. This is done by sending DNS queries to a DNS server, which then responds with the associated record of the domain name in question.