README

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

composer require go-redrock/swiftmailer

Quick Start

SMTP

$transport = new Swift_SmtpTransport('smtp.example.com', 587, 'tls');
$transport->setUsername('user@example.com');
$transport->setPassword('secret');

$mailer = new Swift_Mailer($transport);

$message = (new Swift_Message('Hello'))
    ->setFrom(['sender@example.com' => 'Sender'])
    ->setTo(['recipient@example.com'])
    ->setBody('<h1>Hello!</h1>', 'text/html');

$mailer->send($message);

API Transport (SendGrid)

$transport = new Swift_Transport_Api_SendgridTransport('your-sendgrid-api-key');
$mailer = new Swift_Mailer($transport);
$mailer->send($message);

DSN Factory

$factory = new Swift_Transport_DsnTransportFactory();

// Single transport
$transport = $factory->fromDsnString('sendgrid://API_KEY@default');

// Failover between two providers
$transport = $factory->fromDsnString('failover(sendgrid://KEY@default postmark://KEY@default)');

// Round-robin load balancing
$transport = $factory->fromDsnString('roundrobin(sendgrid://KEY@default postmark://KEY@default)');

// Retry with exponential backoff
$transport = $factory->fromDsnString('retry(sendgrid://KEY@default)');

$mailer = new Swift_Mailer($transport);

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:

$inner = new Swift_Transport_Api_SendgridTransport('SG.your-key');
$transport = new Swift_RetryTransport($inner, maxRetries: 3, baseDelay: 1000);

// Or via DSN
$transport = $factory->fromDsnString('retry(sendgrid://KEY@default)');

Tags and Metadata

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

$message->getHeaders()->addTextHeader('X-Mailer-Tag', 'welcome-email');
$message->getHeaders()->addTextHeader('X-Mailer-Metadata-user_id', '12345');

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

$signer = new Swift_Signers_DKIMSigner($privateKey, 'example.com', 'selector');
$signer->setHashAlgorithm('ed25519-sha256');
// Oversigning of From/To/Subject/Date/Cc/Reply-To/Message-ID is on by default
$message->attachSigner($signer);

Swift_Envelope

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

$envelope = new Swift_Envelope('bounce-handler@example.com', ['actual-recipient@example.com']);
$mailer->send($message, $failedRecipients, $envelope);

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:

./bin/swiftmailer-test 'sendgrid://SG.your-key@default'

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.

Document	Description
doc/introduction.md	Requirements, installation, first email
doc/messages.md	Building messages: bodies, attachments, embedded files, MIME parts
doc/headers.md	Header types and the header set API
doc/sending.md	Transports, `send()`, envelopes, spooling, retries, message limits
doc/api-transports.md	All 21 API transports -- constructors, auth, examples
doc/microsoft-graph.md	Microsoft Graph: auth modes, large attachments, calendar invites
doc/dsn.md	DSN syntax reference and all supported schemes
doc/cli.md	The `swiftmailer-test` CLI tool
doc/events.md	Event lifecycle, listener interfaces, dispatch points
doc/webhooks.md	Webhook processing for delivery and engagement events
doc/plugins.md	All 14 bundled plugins and writing your own
doc/signers.md	DKIM, DomainKeys, and S/MIME signing
doc/security.md	Security hardening: defaults and opt-in protections
doc/architecture.md	Codebase internals for contributors
doc/upgrading.md	Migration guide from stock SwiftMailer 6.x
CONTRIBUTING.md	Dev setup, tests, style, static analysis, CI

License

MIT License. See LICENSE for details.

go-redrock / swiftmailer

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