To request a reply for one item, open an item view, click the Send Options tab, then click General.

or

To request a reply for all items you send, click Tools > Options, then double-click Send.

Click Reply requested, then specify when you want to receive the reply.

The recipient sees next to the message. If you select When Convenient, “Reply Requested: When convenient” appears at the top of the message. If you select Within x Days, “Reply Requested: By xx/xx/xx” appears at the top of the message.

Click OK.