Configure WordPress #wp_mail function to send through #SMTP server https://b.utler.co/Y3

wp_config.php

<?php

/*
 * Set the following constants in wp-config.php.
 * These should be added somewhere BEFORE the constant ABSPATH is defined.
 *
 * Author:     Chad Butler
 * Author URI: https://butlerblog.com
 *
 * For more information and instructions, see: https://b.utler.co/Y3
 */

define( 'SMTP_USER',   '[email protected]' );    // Username to use for SMTP authentication
define( 'SMTP_PASS',   'smtp password' );       // Password to use for SMTP authentication
define( 'SMTP_HOST',   'smtp.example.com' );    // The hostname of the mail server
define( 'SMTP_FROM',   '[email protected]' ); // SMTP From email address
define( 'SMTP_NAME',   'e.g Website Name' );    // SMTP From name
define( 'SMTP_PORT',   '25' );                  // SMTP port number - likely to be 25, 465 or 587
define( 'SMTP_SECURE', 'tls' );                 // Encryption system to use - ssl or tls
define( 'SMTP_AUTH',    true );                 // Use SMTP authentication (true|false)
define( 'SMTP_DEBUG',   0 );                    // for debugging purposes only set to 1 or 2

wp_mail_smtp.php

/**
 * This function will connect wp_mail to your authenticated
 * SMTP server. This improves reliability of wp_mail, and 
 * avoids many potential problems.
 *
 * Values are constants set in wp-config.php. Be sure to
 * define the using the wp_config.php example in this gist.
 *
 * Author:     Chad Butler
 * Author URI: https://butlerblog.com
 *
 * For more information and instructions, see: https://b.utler.co/Y3
 */
add_action( 'phpmailer_init', 'send_smtp_email' );
function send_smtp_email( $phpmailer ) {
	if ( ! is_object( $phpmailer ) ) {
		$phpmailer = (object) $phpmailer;
	}

	$phpmailer->Mailer     = 'smtp';
	$phpmailer->Host       = SMTP_HOST;
	$phpmailer->SMTPAuth   = SMTP_AUTH;
	$phpmailer->Port       = SMTP_PORT;
	$phpmailer->Username   = SMTP_USER;
	$phpmailer->Password   = SMTP_PASS;
	$phpmailer->SMTPSecure = SMTP_SECURE;
	$phpmailer->From       = SMTP_FROM;
	$phpmailer->FromName   = SMTP_NAME;
}

@adeyjones - Yes, you could do it as you described, but I wouldn't go on record as saying that's in any way safe. Ease of implementation should not override security in making decisions. Why not define the settings in a single include file outside the web root. Then every one of your sites could include the same settings when invoking the object.

As far as changes to PHPMailer in WP, the question you need to ask is "Did PHPMailer change the variable names in the object?" The answer to that is "no." This snippet is setting the connection values when the WP action "phpmailer_init" is fired. That of course assumes PHPMailer is already loaded and is being initialized. Whether you need to include the PHPMailer object to begin with depends entirely on the use case in which you are implementing this and is outside the scope of this discussion. (In plain terms, the question has nothing to do with whether this works or not. Don't overthink it.)

Thanks for the reply, glad I don't need to worry about anything other than setting what is needed here.

So when you said include a file outside the web root, did you mean perhaps including the settings in a PHP file in the hosting account for my main website perhaps (example.com/file.php) and then include that in my 160+ sites (I assume including an external file in functions.php is allowed?)

If you save it in another site, that's still the web root for that site. I'm talking about keeping it outside your web root. BTW, you can do that for the entire wp config as well. See: https://wordpress.stackexchange.com/questions/58391/is-moving-wp-config-outside-the-web-root-really-beneficial

This doesn't work for me. I've implemented exactly as shown, but I get this:

`[0] => Invalid address:  (From): wordpress@localhost`

I was forced to implement these hooks as well:

add_filter('wp_mail_from', 'set_wp_mail_from');
function set_wp_mail_from($current_from) {
	if (SMTP_FROM) { 
		return SMTP_FROM;
	}
	throw new Exception('SMTP_FROM not detected...');
}

add_filter('wp_mail_from_name', 'set_wp_mail_from');
function set_wp_mail_from_name($current_from_name) {
	if (SMTP_NAME) {
		return SMTP_NAME;	
	}
	throw new Exception('SMTP_NAME not detected...');
}