public function validate() {
		$retval = true;

		// BCC, CC, and token properties are optional.
		if (
			! $this->get_from() ||
			! $this->get_to() ||
			! $this->get_subject() ||
			! $this->get_content() ||
			! $this->get_template()
		) {
			$retval = new WP_Error( 'missing_parameter', __CLASS__, $this );
		}

		/**
		 * Filters whether the email passes basic validation checks.
		 *
		 * @since 2.5.0
		 *
		 * @param bool|WP_Error $retval Returns true if validation succesful, else a descriptive WP_Error.
		 * @param BP_Email $this Current instance of the email type class.
		 */
		return apply_filters( 'bp_email_validate', $retval, $this );
	}