public function set_subject( $subject ) {

		/**
		 * Filters the new value of the subject email property.
		 *
		 * @since 2.5.0
		 *
		 * @param string $subject Email subject.
		 * @param BP_Email $this Current instance of the email type class.
		 */
		$this->subject = apply_filters( 'bp_email_set_subject', $subject, $this );

		return $this;
	}