The SMTP Transport class (named Swift_SmtpTransport) is used when you want to send messages using an SMTP server. Before you decide to use this Transport method you first need to know the credentials to connect to an SMTP server from your web host. Most web hosts provide an SMTP server to use, others do not. Some SMTP servers will require the use of a username and password before you can send.

The Swift_SmtpTransport class take several (optional) parameters in its constructor.

Synopsis

new Swift_SmtpTransport( [ $host [, $port [, $security ] ] ] )

// or

Swift_SmtpTransport::newInstance( [ $host [, $port [, $security ] ] ] )

$host is the domain name of the SMTP server. This is typically mail.isp.tld or smtp.isp.tld where “isp.tld” is your ISP‘s domain. For example, BigPond here in Australia use the domain “bigpond.com.au” and their SMTP server is “mail.bigpond.com.au”. The default value for $host is “localhost” and will work on some web hosts.

$port is the port number you connect to the SMTP server on. The standard SMTP port is 25. SMTP servers using SSL encryption will often use port 587 or port 465. Swift will default to port 25 if no port number is specified.

$security is an encryption setting. If your ISP requires the use of SSL then you should specify “ssl” here. If they require TLS then you should specify “tls” here. Otherwise, a value of “none” indicates that no security layer is used. Swift defaults to “none”.

If your ISP have told you that you need to authenticate with the SMTP server then you will need to tell Swift what username and password to use. $smtp→setUsername(”your username”) and $smtp→setPassword(”your password”) are used for this. You need to create $smtp into a variable first. See the last few examples below...

$smtp = new Swift_SmtpTransport('mail.bigpond.com.au', 25);
 
$mailer = new Swift_Mailer($smtp);
 
$message = new Swift_Message('My Subject', 'My message body');
$message->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'));
$message->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);

//You can use the newInstance() method instead of declaring "new"
$smtp = Swift_SmtpTransport::newInstance('mail.bigpond.com.au', 25);
 
$mailer = new Swift_Mailer($smtp);
 
$message = new Swift_Message('My Subject', 'My message body');
$message->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'));
$message->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);

//You can nest the instantiation of the SmtpTransport instead of creating a $smtp variable
$mailer = new Swift_Mailer(new Swift_SmtpTransport('smtp.mycompany.com', 587, 'ssl'));
 
//You can set fields on $message fluidly everywhere in Swift
$message = Swift_Message::newInstance('My Subject', 'My message body')
  ->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'))
  ->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);

$mailer = new Swift_Mailer(new Swift_SmtpTransport()); //Default: localhost port 25
 
$message = Swift_Message::newInstance('My Subject', 'My message body')
  ->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'))
  ->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);

$smtp = new Swift_SmtpTransport('smtp.mycompany.com');
 
//Specify a username and password
$smtp->setUsername('n00bie');
$smtp->setPassword('p4s5w0rd');
 
$mailer = new Swift_Mailer($smtp);
 
$message = Swift_Message::newInstance('My Subject', 'My message body')
  ->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'))
  ->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);

//Setting a username and password fluidly
$smtp = Swift_SmtpTransport::newInstance('smtp.mycompany.com')
  ->setUsername('n00bie')
  ->setPassword('p4s5w0rd');
 
$mailer = new Swift_Mailer($smtp);
 
$message = Swift_Message::newInstance('My Subject', 'My message body')
  ->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'))
  ->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);

//When using the fluid interface you can nest an authenticated SmtpTransport
$mailer = new Swift_Mailer(
  Swift_SmtpTransport::newInstance('smtp.mycompany.com')
    ->setUsername('n00bie')
    ->setPassword('p4s5w0rd')
  );
 
$message = Swift_Message::newInstance('My Subject', 'My message body')
  ->setFrom(array('chris.corbyn@swiftmailer.org' => 'Chris Corbyn'))
  ->setTo(array('recipient@otherdomain.tld' => 'Recipient name'));
 
$mailer->send($message);