Hooks in order to customize WordPress WP Mail headers.

customize-wp-mail.php

<?php class MC_Customize_WP_Mail {

	private $sender_mail;
	private $sender_name;
	private $reply_mail;
	private $replay_name;

    /**
	 * Set custom sender mail and name for all sent emails
	 * and add a reply to mail and name to allow people replying to your sent emails
	 *
	 * MC_Customize_WP_Mail constructor.
	 *
	 * @param $sender_mail
	 * @param $sender_name
	 * @param $reply_mail
	 * @param $replay_name
	 *
	 * @author Maxime Culea
	 */
	public function __construct( $sender_mail, $sender_name, $reply_mail, $replay_name ) {
		$this->sender_mail = $sender_mail;
		$this->sender_name = $sender_name;
		$this->reply_mail  = $reply_mail;
		$this->replay_name = $replay_name;
	}

	public function _init() {
		// set higher priority for overwritting settings from others plugins
		add_filter( 'wp_mail_from', [ $this, 'set_sender_mail' ], 999 );
		add_filter( 'wp_mail_from_name', [ $this, 'set_sender_name' ], 999 );
		add_filter( 'wp_mail', [ $this, 'set_reply_to' ] );
	}

	/**
	 * Change sender mail with the provided one
	 *
	 * @param string $original_sender_mail
	 *
	 * @author Maxime Culea
	 *
	 * @return string
	 */
	function set_sender_mail( $original_sender_mail ) {
		return $this->sender_mail ?: $original_sender_mail;
	}

	/**
	 * Change sender name with the provided one
	 *
	 * @param string $original_sender_name
	 *
	 * @author Maxime Culea
	 *
	 * @return string
	 */
	function set_sender_name( $original_sender_name ) {
		return $this->sender_name ?: $original_sender_name;
	}

	/**
	 * Change the Reply To headers with the provide one, if it doesn't exist
	 *
	 * @param array $args
	 *
	 * @author Maxime Culea
	 *
	 * @return array
	 */
	function set_reply_to( $args ) {
		if ( empty( $this->replay_name ) || empty( $this->reply_mail ) ) {
			return $args;
		}

		if ( ! isset( $args['headers'] ) ) {
			$args['headers'] = [];
		}

		// Does it exist already?
		if ( stripos( serialize( $args['headers'] ), 'Reply-To:' ) !== false ) {
			return $args;
		}

		$reply_to_line = sprintf( "Reply-To: %s <%s>", $this->replay_name, $this->reply_mail );
		if ( is_array( $args['headers'] ) ) {
			$args['headers'][] = 'h:' . $reply_to_line;
			$args['headers'][] = $reply_to_line . "\r\n";
		} else {
			$args['headers'] .= 'h:' . $reply_to_line . "\r\n";
			$args['headers'] .= $reply_to_line . "\r\n";
		}

		return $args;
	}
}

// Here emails will be sent from MC Website <[email protected]> and people will reply to Maxime Culea <[email protected]>
$mccwpm = new MC_Customize_WP_Mail( '[email protected]', 'MC Website', '[email protected]', 'Maxime Culea' );
$mccwpm->_init();