mail

Imported from nette/mail (AGENTS.md). Install upstream with npx skills add nette/mail. Copyright stays with the author.

To My Agents!

It is my fervent wish that this file guide every AI coding agent working with code in this repository.

Documentation

Any distilled, agent-facing documentation for this package - how it works internally and the rationale behind key design decisions - lives in docs/. Consult it before non-trivial changes; it is the source of truth from which the public manual is distilled.

Project Overview

Nette Mail is a standalone PHP library for creating and sending emails with support for SMTP, sendmail, DKIM signing, and fallback mechanisms. Part of the Nette Framework ecosystem but usable independently.

• Requirements: PHP 8.2 - 8.5, ext-iconv required
• Optional extensions: ext-dom (CssInliner, PHP 8.4+), ext-fileinfo (attachment type detection), ext-openssl (DKIM signing)
• Main dependency: nette/utils ^4.1

Essential Commands

Testing

# Run all tests
composer run tester
# or
vendor/bin/tester tests -s

# Run specific test file
vendor/bin/tester tests/Mail/Message.phpt -s

# Run tests in specific directory
vendor/bin/tester tests/Mail/ -s

Static Analysis

# Run PHPStan analysis (level 8)
composer run phpstan
# or
vendor/bin/phpstan analyse

Architecture

Core Components

The library consists of five main areas:

1. Email Creation (src/Mail/)

   • Message - Main class for composing emails, extends MimePart
   • MimePart - Base class handling MIME encoding, headers, and structure
   • HtmlComposer - Pipeline behind setHtmlBody(): optional CSS inlining and image embedding, subject from <title>, plain-text alternative generation
   • Priority constants: Message::High, Message::Normal, Message::Low

2. Email Sending (src/Mail/)

   • Mailer interface - Contract for all mailer implementations
   • SendmailMailer - Uses PHP's mail() function
   • SmtpMailer - Full SMTP protocol implementation with TLS/SSL support
   • FallbackMailer - Retry mechanism across multiple mailers
   • Interceptor - Wraps any Mailer with optional redirect of outgoing emails to a fixed address (debugging/safety) and an $onSent event fired after each send (success or failure)

3. Email Signing (src/Mail/)

   • Signer interface - Contract for signing implementations
   • DkimSigner - DKIM (DomainKeys Identified Mail) signing using RSA-SHA256

4. CSS Inlining (src/Mail/)

   • CssInliner - Converts CSS rules to inline style attributes for email HTML (requires PHP 8.4+ for Dom\HTMLDocument)

5. Tracy Bar Panel (src/Bridges/MailTracy/)

   • MailPanel - IBarPanel showing sent emails in the Tracy Bar; subscribes to Interceptor::$onSent

Dependency Injection Integration

src/Bridges/MailDI/MailExtension.php - Nette DI compiler extension for configuration.

DI Services registered:

• mail.mailer - autowired public Mailer; either the real transport directly (SendmailMailer/SmtpMailer) or, when redirect or debugger: true is configured, an Interceptor wrapping the real transport
• mail.innerMailer - private real transport (only present when mail.mailer is an Interceptor)
• mail.signer - DKIM Signer instance (only when DKIM is configured)
• mail.panel - MailPanel Tracy Bar panel (only in debug mode when the Interceptor is active and Tracy\Bar is registered)
• nette.mailer - alias to mail.mailer (for backward compatibility)

Configuration:

mail:
	# Use SmtpMailer instead of SendmailMailer
	smtp: true              # (bool) defaults to false

	# SMTP connection settings
	host: smtp.gmail.com    # (string) SMTP server hostname
	port: 587               # (int) defaults: 465 for ssl, otherwise 25
	username: user@example.com
	password: ****
	encryption: tls         # (ssl|tls|null) null = no encryption
	timeout: 20             # (int) connection timeout in seconds, default 20
	persistent: false       # (bool) use persistent connection
	clientHost: localhost   # (string) defaults to $_SERVER['HTTP_HOST'] or 'localhost'

	# SSL/TLS context options for SMTP connection
	context:
		ssl:
			verify_peer: true           # NEVER set to false in production!
			verify_peer_name: true
			allow_self_signed: false    # Do not allow self-signed certificates
			# See https://www.php.net/manual/en/context.ssl.php for all options

	# DKIM signing configuration
	dkim:
		domain: example.com             # Your domain name
		selector: dkim                  # DKIM selector from DNS
		privateKey: %appDir%/../dkim/private.key  # Path to private key file
		passPhrase: ****                # Optional passphrase for private key

	# Redirect all outgoing emails to a fixed address (debugging/safety)
	# Shortcut form: just the address
	redirect: dev@example.com
	# Or full form with subject prefix:
	# redirect:
	#     to: dev@example.com
	#     subjectPrefix: '[debug]'

	# Tracy panel:
	#  - default: attached when Interceptor is active, in debug mode, and Tracy\Bar exists
	#  - 'debugger: true' explicitly opts in (and forces Interceptor wiring even without redirect)
	#  - 'debugger: false' explicitly opts out
	debugger: true

Security Warning: Never disable SSL certificate verification (verify_peer: false) as it makes your application vulnerable to man-in-the-middle attacks. Instead, add certificates to the trust store if needed.

Exception Hierarchy

All exceptions in src/Mail/exceptions.php:

• SendException - Base exception for sending failures
• SmtpException - SMTP-specific errors (extends SendException)
• FallbackMailerException - All mailers failed (contains array of failures)
• SignException - Signing/verification errors

Key Features

Message Creation:

• Fluent API with method chaining
• Automatic text alternative generation from HTML
• Auto-embedding images from filesystem using [[...]] syntax or <img src=...>
• Subject auto-extraction from <title> element
• Attachment support with auto-detection of MIME types

MIME Handling:

• Encoding methods: Base64, 7bit, 8bit, quoted-printable
• Line length management (76 characters default)
• Full UTF-8 support throughout

SMTP Features:

• TLS/SSL encryption support (encryption: 'ssl' or 'tls')
• Default ports: 465 (SSL), otherwise 25 (incl. TLS/STARTTLS; set port: 587 explicitly for submission)
• Persistent connections
• Configurable timeout (default 20s)
• Custom stream options for SSL context
• Envelope sender support
• AUTH PLAIN and LOGIN authentication methods

DKIM Signing:

• RSA-SHA256 signing algorithm
• Private key passphrase support
• Automatic header canonicalization
• Compatible with Gmail, Outlook, and other major providers

Testing Strategy

Uses Nette Tester with .phpt format:

<?php
declare(strict_types=1);

use Tester\Assert;

require __DIR__ . '/../bootstrap.php';

test('Message correctly sets recipient', function () {
	$mail = new Nette\Mail\Message;
	$mail->addTo('test@example.com');

	Assert::same(['test@example.com' => null], $mail->getHeader('To'));
});

• Test files in tests/Mail/ cover all major functionality
• Test fixtures in tests/Mail/fixtures/ for email samples
• Bootstrap in tests/bootstrap.php provides test() helper function
• Tests run on PHP 8.2-8.5 in CI

Coding Standards

Follows Nette Coding Standard (PSR-12 based) with these requirements:

• Mandatory: declare(strict_types=1) in all PHP files
• Indentation: Tabs (not spaces)
• Method spacing: Two empty lines between methods
• Types: All properties, parameters, and return values must be typed
• Documentation: Only when adding information beyond PHP types
  • Document array contents: @return string[]
  • Document nullable relationships: @param ?string
  • Skip obvious parameters (width, height, name)
• String quotes: Single quotes unless containing apostrophes
• Naming: PascalCase for classes, camelCase for methods/properties
• No prefixes: No Abstract, Interface, or I prefixes

Return Type Format

Opening brace on separate line after return type:

public function send(Message $mail): void
{
	// method body
}

phpDoc Examples

/**
 * Adds email recipient. Email or format "John Doe" <doe@example.com>
 */
public function addTo(string $email, ?string $name = null): static

/**
 * Sets a header.
 * @param  string|array<string, ?string>|null  $value  value or pair email => name
 */
public function setHeader(string $name, string|array|null $value, bool $append = false): static

Development Workflow

1. Before making changes:

   • Read existing code to understand patterns
   • Check related test files
   • Verify PHPStan passes: composer run phpstan

2. When adding features:

   • Add corresponding tests in tests/Mail/
   • Use test() helper for test cases
   • Run tests: vendor/bin/tester tests -s

3. When fixing bugs:

   • Add regression test first
   • Ensure fix doesn't break existing tests
   • Update PHPDoc if behavior changes

4. Before committing:

   • Run full test suite: composer run tester
   • Run static analysis: composer run phpstan
   • Check code style with Nette Code Checker

Usage in Nette Application

When using Nette Mail within a full Nette Application (with presenters), you can integrate it with Latte templates and create absolute links using LinkGenerator.

Email Templates with Links

To use n:href and {link} in email templates, inject both TemplateFactory and LinkGenerator:

use Nette;

class MailSender
{
	public function __construct(
		private Nette\Application\LinkGenerator $linkGenerator,
		private Nette\Bridges\ApplicationLatte\TemplateFactory $templateFactory,
	) {
	}


	private function createTemplate(): Nette\Application\UI\Template
	{
		$template = $this->templateFactory->createTemplate();
		// Add LinkGenerator as 'uiControl' provider for n:href and {link}
		$template->getLatte()->addProvider('uiControl', $this->linkGenerator);
		return $template;
	}


	public function sendOrderConfirmation(int $orderId): void
	{
		$template = $this->createTemplate();
		$html = $template->renderToString(__DIR__ . '/templates/orderEmail.latte', [
			'orderId' => $orderId,
		]);

		$mail = new Nette\Mail\Message;
		$mail->setFrom('shop@example.com')
			->addTo('customer@example.com')
			->setHtmlBody($html);

		$this->mailer->send($mail);
	}
}

Template with absolute links:

<p>Your order #{$orderId} has been confirmed.</p>
<p><a n:href="Order:detail $orderId">View order details</a></p>

All links created via LinkGenerator are absolute (include full domain), which is required for emails.

Important Patterns

Encoding

• All input strings must be valid UTF-8 (setHeader validates via Strings::checkEncoding and throws otherwise)
• Non-ASCII header values are encoded as RFC 2047 base64 encoded-words
• Body transfer encoding (7bit/8bit/quoted-printable) is chosen automatically by content sniffing

Header Management

• Header names are stored and looked up case-sensitively, exactly as passed to setHeader()/getHeader() (use the canonical To, Content-Type, ... spelling)
• Email headers (To, Cc, Bcc, From, Reply-To) are stored as [email => name] arrays; each address is validated
• setHeader strips \r\n from values - it is the injection-prevention boundary

Image Embedding

Automatic embedding supports:

• <img src="...">
• <body background="...">
• CSS url(...) in style attributes
• Special [[filename]] syntax

SendmailMailer Configuration

SendmailMailer uses PHP's mail() function. The envelope sender (-f option) is set automatically from the From header; disable with setEnvelopeSender(false) or pass custom arguments:

$mailer = new Nette\Mail\SendmailMailer;
$mailer->commandArgs = '-fmy@email.com';  // Set return path manually

SMTP Connection

SmtpMailer handles SMTP protocol details:

• Automatic STARTTLS negotiation
• AUTH PLAIN and LOGIN support
• Proper QUIT handling in persistent mode
• Full error message parsing
• Connection reuse with persistent mode

CSS Inlining

CssInliner converts CSS rules to inline style attributes for email HTML compatibility. Uses Dom\HTMLDocument (PHP 8.4+) for DOM manipulation and CSS selectors.

// From <style> tags in HTML (automatically extracted, tag preserved)
$html = (new CssInliner)->inline($html);

// External CSS string
$html = (new CssInliner)->addCss('p { margin: 0; }')->inline($html);

Architecture:

• Single-regex tokenizer (comment, whitespace, string, url, escape, at-ident, hash, number, ident, char)
• Token-based stylesheet parser with CSS nesting and @-rule skipping
• Declarations parsed into property => value arrays (enables deduplication and HTML attribute generation)
• Cascade: <style> → addCss() → existing inline style="" wins (last declaration wins)
• <style> tags are preserved (keeps @media queries intact)
• Automatic HTML attribute generation for Outlook compatibility (background-color→bgcolor, width→width, height→height, border-spacing→cellspacing; align/valign intentionally excluded, their semantics differ from CSS)