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Swift Mailer

A component-based PHP mailing library, maintained by Redrock Software Corporation. This fork integrates features from Symfony Mailer back into SwiftMailer for legacy and enterprise applications that cannot migrate to Symfony Mailer.

About This Fork

The original SwiftMailer was abandoned by its creators in November 2021. Redrock Software Corporation picked up maintenance in 2022 to serve the many legacy and enterprise PHP applications that depend on SwiftMailer and cannot practically migrate to Symfony Mailer.

What We've Done

Since taking over, Redrock has shipped a major modernization of SwiftMailer (v6.4.0) that back-ports the most valuable Symfony Mailer capabilities while preserving full backward compatibility:

• 21 HTTP API transports -- SendGrid, Mailgun, Postmark, Brevo, Amazon SES, Azure, Gmail API, Microsoft Graph, Resend, Scaleway, InfoBip, MailPace, Mandrill, MailerSend, Mailjet, AhaSend, Mailomat, Mailtrap, Postal, Sweego, and more
• DSN transport factory -- create any transport from a connection string, with failover(), roundrobin(), and retry() wrappers
• Webhook system -- process inbound delivery/bounce/engagement webhooks from 14 providers with signature verification
• New events -- SentMessageEvent and FailedMessageEvent for post-send tracking
• New plugins -- AllowlistPlugin (dev/staging safety), CssInlinerPlugin (auto CSS inlining), SentMessagePlugin (post-send inspection), ReadReceiptPlugin (MDN read receipts + tracking pixel)
• DKIM enhancements -- Ed25519-SHA256 signing, header oversigning
• SMTP improvements -- Auto TLS, Smart SMTPUTF8, explicit envelope control via Swift_Envelope
• RetryTransport -- automatic retries with exponential backoff for any transport
• Security hardening -- #[SensitiveParameter] on API keys, Guzzle exception sanitization, serialization blocking
• Modern tooling -- PHP 8.3+ baseline, PHPStan static analysis, CI pipeline with GitHub Actions, Infection mutation testing, PHP-CS-Fixer
• CLI test tool -- bin/swiftmailer-test for validating transport configuration from the command line

The Future of SwiftMailer

SwiftMailer is not dead -- it's actively maintained and developed. Our roadmap includes:

• Continued Symfony Mailer parity -- closing the remaining feature gaps (see docs/SYMFONY_MAILER_PARITY.md)
• Additional API transports -- expanding provider coverage as new services emerge
• PHP version support -- staying current with the latest PHP releases
• Community contributions -- we welcome pull requests, bug reports, and feature requests

If your application uses SwiftMailer, you don't have to migrate. Upgrade to this fork and get modern features with zero code changes to your existing mail code.

Requirements

• PHP 8.3+
• Extensions: iconv, mbstring, intl, openssl

Installation

Quick Start

SMTP

API Transport (SendGrid)

DSN Factory

Features

21 HTTP API Transports

SendGrid, Mailgun, Postmark, Brevo, Amazon SES (API + HTTP), Azure Communication Services, Google Gmail API, Microsoft Graph, Resend, Scaleway, InfoBip, MailPace, MailChimp/Mandrill, MailerSend, Mailjet, AhaSend, Mailomat, Mailtrap, Postal, Sweego.

See doc/api-transports.md for constructor arguments, authentication, and examples.

DSN Transport Factory

Create any transport from a connection string. Supports failover(), roundrobin(), and retry() wrappers for redundancy, load balancing, and automatic retries with exponential backoff.

See doc/dsn.md for the full scheme reference.

RetryTransport

Wrap any transport with automatic retry logic featuring exponential backoff:

Tags and Metadata

Attach tags and metadata to messages via headers. API transports automatically map them to each provider's native format.

See doc/api-transports.md for provider-specific mapping details.

Webhook System

Process inbound webhooks from 14 email providers to track deliveries, bounces, opens, clicks, and complaints. Supported providers: SendGrid, Mailgun, Postmark, Amazon SES, Brevo, Resend, MailerSend, Mailjet, Mandrill, AhaSend, Mailomat, Mailtrap, Sweego, MailPace.

See doc/webhooks.md for setup and provider-specific examples.

New Plugins

• AllowlistPlugin -- restrict delivery to allowed recipients/domains with descriptive rejection reasons (dev/staging safety)
• CssInlinerPlugin -- automatically inline CSS in HTML emails before sending
• SentMessagePlugin -- capture Swift_SentMessage objects for post-send inspection
• ReadReceiptPlugin -- toggleable MDN read receipts and/or tracking-pixel injection

See doc/plugins.md for configuration and usage.

New Events

• SentMessageEvent -- fired after successful send, carries Swift_SentMessage with provider message ID
• FailedMessageEvent -- fired on send failure, carries exception and failed recipient list

See doc/events.md for the complete event lifecycle.

DKIM Signing

Enhanced DKIM signer with support for:

• Ed25519-SHA256 algorithm (ed25519-sha256) in addition to RSA-SHA256
• Oversigning of From, Subject, and other headers to prevent header injection
• Modernized API with fluent configuration

Swift_Envelope

Explicit SMTP envelope control, separating the SMTP envelope sender/recipients from the message headers:

SMTP Enhancements

• Auto TLS -- STARTTLS negotiation mode alongside traditional ssl/tls
• Smart SMTPUTF8 -- AutoAddressEncoder detects SMTPUTF8 server capability and switches encoding automatically
• DSN parameters -- verify_peer, peer_fingerprint, source_ip, smtputf8 via DSN query string

Security Hardening

• #[SensitiveParameter] on all API key constructor parameters (PHP 8.2+)
• Guzzle exception chain sanitized to prevent API key leakage in stack traces
• Serialization blocked on transport objects (__sleep/__wakeup throw)

CLI Testing Tool

The bin/swiftmailer-test command-line tool validates your transport configuration:

CI & Quality

• GitHub Actions CI pipeline with a PHP 8.3--8.5 test matrix
• GitLab CI pipeline with unit tests (PHP 8.3/8.5), Mailpit smoke tests, and Infection mutation testing
• PHPStan level 5 static analysis
• PHP-CS-Fixer code style enforcement

Documentation

The complete documentation lives in doc/ -- no external docs site required.

Sponsors

License

MIT License. See LICENSE for details.