README

Simple services for sending UTF-8 e-mail.

See UPGRADING.md for upgrade instructions.

Features

• SMTP client supports username/password authentication and secure (SSL) sockets.
• Sends MIME-compliant multi-part text/HTML e-mails.
• Handles large attachments using streams for predictable, low memory usage.
• Attachments from memory or from any stream-wrapper.
• Support for inline (image) attachments.
• Multiple recipients for all types of recipient fields.
• Sends multiple e-mails without reconnecting.

Non-Features

Some features are delibarely outside the scope of this project:

• Support for arbitrary character sets is omitted - all modern mail clients support UTF-8.

• No support for mail() as a transport method, as this function has constraints that conflict with our objectives - mainly, it does not support streams, which means the entire message has to fit in memory, which leads to unpredictable performance and memory usage.

Overview

Mail service implementations are abstracted behind the MailService interface, which depends on the Message model to define the actual content.

To send mail, simply create an instance of Message, populate it with new instances of Address and Attachment models by calling various public set/add-methods, then call MailService::send().

The model permits any combination of UTF-8 text and HTML message bodies with any number of attachments.

Usage

The following example assumes a MailService instance named $service is in scope - subsequent sections will explain how to configure an e-mail service.

Here's an example of sending a plain-text e-mail with an attachment:

$message = new Message(
    new Address($email),        // recipient
    new Address("me@test.org"), // sender
    "Hello, Person!",           // subject
    $text                       // plain text message body
);

$message->addAttachment(Attachment::fromFile(__DIR__ . "/awsum/unicorns.gif"));

$service->send($message);

Refer to the Message model to learn about additional message properties.

SMTP Mail Service

The SMTPMailService implementation connects directly to an SMTP server via sockets.

To bootstrap an SMTP mail service, you need to select your Connector and Authenticator implementations - for example:

$service = new SMTPMailService(
    new SocketConnector("localhost", 25),
    new LoginAuthenticator("user", "super_secret_pa55w0rd"),
    "test.org"
);

Note the third argument, which is the local host-name - this is used in the handshake (EHLO) message send to the SMTP server when the client connects.

SMTP protocol-level logging is supported for diagnostic purposes, and can be enabled by injecting a PSR-3 Logger into SMTPClient via SMTPClient::setLogger() - this may be useful if you have connection issues, as it will write a debug-level entry for every SMTP command sent, and every response received.

Message Logging

Unlike SMTP protocol-level logging described above, a more general logging facility is also available - this will write a single log-entry on success or failure to send a message, and is more generally applicable to any MailService implementation, including of course the SMTP service.

To write a log-entry to a PSR-3 Logger, use the MailSeviceLogger implementation, which acts as a decorator for any other MailService implementation - for example:

$service = new MailServiceLogger($psr_logger, new SMTPMailService(...));

See inline documentation for MailServiceLogger for details on customizing the message template and log-level.

Passive Mail Service

A passive implementation of MailService is available, which does nothing.

You can use this during testing/development to disable any outgoing Messages.

This is typically most useful in conjunction with the MailServiceLogger described above, to bootstrap a fake mail-service for testing and development, enabling you to see Messages that would have been sent.

Development

To run the integration tests, you will need to set up a local SMTP server for testing.

To make sure SecureSocketCest passes your SMTP server also needs to have TLS support with a SSL certificate.

It is recommended to use smtp4dev since it has cross-platform support and can generate its own self-signed SSL certificate.

When configuring smtp4dev make sure to set TlsMode to StartTls, this ensures that TLS is only used when the client asks for it, setting it to ImplicitTls will likely make all non-TLS tests fail.

When starting the smtp4dev server it should tell you where the generated certificate is stored, you'll need to add this to your systems trusted CA store.

You may need to copy integration.suite.dist.yml to integration.suite.yml to customize the SMTP host-name, port-number, etc.

Objectives

This library has a number of stated design objectives:

• Simplicity: UTF-8 is the only supported character-set, we make an effort not to reinvent the wheel (e.g. leveraging base64 and quoted-printable stream-filters) and the library has no external dependencies.
• Using streams for efficiency and predictable memory usage - in particular, file attachments are encoded and sent in chunks, without buffering the entire message or juggling huge strings.
• Separation of concerns - in particular, MIME encoding and SMTP transport concerns ("dot-stuffing") are fully separated, which in turn is made possible by proper use of streams.
• Using dependency injection (primarily constructor injection) everywhere.
• Using abstractions (interfaces) both at the high level and for dependencies/components.