Hi,

If you want to enable option for "sent to mail recipient" follow these steps:
1.    Open the form in Design mode.
2.    Go to Tools menu and select Form Options.
3.    Click on “Open and save” tab order in the Form Options box.
4.    Check “Send to mail Recipient” check box and click on ok.
5.    Publish it to Shared or share point location.
6.    Now open the form.
7.    “Send to mail Recipient” option is enabled in the File menu.

I hope this will help you.