Sending a Mail with a Callback Function 
Use
You can send calls with a note or as an attachment to a document. The recipient can then call you back by calling the document or the attachment. The callback function can only be used by SAP users whose telephony settings are maintained.

An employee cannot be reached by telephone at the moment. You can send a mail to the employee asking them to call you back and append an executable call to your telephone number to the mail and send it. When the recipient calls up the attachment, the Initiate call dialog box containing the specified number is displayed.
Procedure
Wait until the system has opened a new session.
2. Specify the title of the document and enter a text.
A list of the available objects is displayed.
The tab page Attachments is added to the tab pages Document content and Attributes.
.Result
The message is placed in the Business Workplace inbox of the recipients. They can call the message there. If they call up the attachment and confirm the dialog box, the callback is initiated.