Question

I’m trying to send an email with the following function as a test function:

function SendEmail($to, $subject, $body, $headers)
{
    ini_set("SMTP", "smtp.myexistingdomain.com");
    mail($to, $subject, $body, $headers);
}

and I get this error:

Warning: mail() [function.mail]: Failed to connect to mailserver at
“smtp.myexistingdomain.com” port 25, verify your “SMTP” and
“smtp_port” setting in php.ini or use ini_set()

Answer 1

PHP doesn’t implement SMTP protocol. PHP’s mail() – is wrapping around sendmail binary. Works fine on unix/linux.
But On Windows (from PHP.net manual):

The Windows implementation of mail() differs in many ways from the
Unix implementation. First, it doesn’t use a local binary for
composing messages but only operates on direct sockets which means a
MTA is needed listening on a network socket (which can either on the
localhost or a remote machine).

So – the moral of the story – you need to install mail server.

If you prefer to send emails without installing you own mailserver (which can be a pain in the *ss) – you must use a library that actually implements SMTP protocol and thus allows you to connect to someone else SMTP server.
These are most popular nowadays:

1. PHPmailer (download)
2. Swiftmailer
3. Zend_Mail

Using these libraries one can construct text or html messages with ease. Adding files also becomes an easy thing to do.

/*******************************************************************
  Example of sending email using gmail.com SMTP server and phpmailer
*******************************************************************/
$mail = new PHPMailer();  // create a new object
$mail->IsSMTP(); // enable SMTP
$mail->SMTPDebug = 0;  // debugging: 1 = errors and messages, 2 = messages only
$mail->SMTPAuth = true;  // authentication enabled
$mail->SMTPSecure = 'ssl'; // secure transfer enabled REQUIRED for Gmail
$mail->Host = 'smtp.gmail.com';
$mail->Port = 465; 
$mail->Username = GUSER;  
$mail->Password = GPWD;           
$mail->SetFrom($from, $from_name);
$mail->Subject = $subject;
$mail->Body = $body;
$mail->AddAddress($to);
if(!$mail->Send()) {
    $error = 'Mail error: '.$mail->ErrorInfo; 
    return false;
} else {
    $error = 'Message sent!';
    return true;
}