SMTP

The SMTP component implements an RFC 5321 SMTP client with connection pooling, TLS, authentication, and support for modern SMTP extensions. It integrates with the Message and MIME components for complete email sending.

Sending a Message

The Transport handles the full SMTP lifecycle: connection, EHLO, TLS, authentication, message transmission, and connection reuse. Pass an Envelope (derived from message headers) and a MessageInterface to send.

@example('protocols/smtp-basic.php')

Authentication

Five authentication mechanisms are supported. Pass any AuthenticatorInterface as the second argument to Transport.

@example('protocols/smtp-auth.php')

Transport Configuration

TransportConfiguration controls connection-level settings: host, port, security mode, pipelining, chunking, and TCP/TLS options. All settings are immutable with fluent with*() builders.

@example('protocols/smtp-config.php')

Send Configuration

SendConfiguration controls per-send MAIL FROM extension parameters: DSN notifications, REQUIRETLS, message priority, delivery deadlines, and deferred delivery.

@example('protocols/smtp-send-config.php')

Partial Recipient Success

By default, the transport throws on the first rejected recipient. Enable allowPartialSuccess to deliver to accepted recipients and report failures via DeliveryReport.

@example('protocols/smtp-partial.php')

Async and Cancellation

The transport is fully async-capable. Use Async\concurrently to send multiple messages in parallel with automatic connection pooling. Use cancellation tokens for timeouts.

@example('protocols/smtp-async.php')

Low-Level Connection

Connection implements Network\StreamInterface and speaks raw SMTP commands. Use it for direct protocol interaction or to build custom transports.

@example('protocols/smtp-connection.php')

SMTP Extensions

The transport automatically negotiates these extensions when the server advertises them:

Security

The transport validates all SMTP commands for CRLF and null byte injection attacks. Malicious input in addresses, hostnames, or DSN parameters throws PossibleAttackException before reaching the wire.

See src/Psl/SMTP/ for the full API.