BP_Email::set_to( string|array|int|WP_User $to_address, string $name = '', string $operation = 'replace' )

	public function set_to( $to_address, $name = '', $operation = 'replace' ) {
		$to = ( $operation !== 'replace' ) ? $this->to : array();

		if ( is_array( $to_address ) ) {
			foreach ( $to_address as $address ) {
				$to[] = new BP_Email_Recipient( $address );
			}

		} else {
			$to[] = new BP_Email_Recipient( $to_address, $name );
		}

		/**
		 * Filters the new value of the email's "to" property.
		 *
		 * @since BuddyPress 2.5.0
		 *
		 * @param BP_Email_Recipient[] "To" recipients.
		 * @param string $to_address "To" address.
		 * @param string $name "To" name.
		 * @param string $operation If "replace", $to_address replaced previous recipients. If "add",
		 *                          $to_address was added to the array of recipients.
		 * @param BP_Email $this Current instance of the email type class.
		 */
		$this->to = apply_filters( 'bp_email_set_to', $to, $to_address, $name, $operation, $this );

		return $this;
	}