Please reply by return.

请尽快回复。

Please answer her letter by return.

请把给她的回信随下一班邮件寄来。

Please send them by return of mail.

请发送的邮件返回。

Please let us know your answer by return.

请在下一班回程邮递寄回你的答复。

Your reply by return of post will be appreciated.

如能回信答复，将甚为感谢。