Receipts

The Receipts Settings window:

Requesting Read Receipts

Check the Request a read receipt for all sent messages box, to have an auto-generated confirmation message sent back to you when the recipient of your messages have opened and read your messages.

Returning Read Receipts 

Here you can specify whether you wish to Never send a read receipt, have eM Client prompt you whether you wish to send a read receipt or always send a read receipt for your incoming emails.