Thanks for confirming that question for me.
An unsending function for emails that have been sent, is not a very common feature in most email application or service.
Such email service which can allow you to unsend (or destroy
) emails after you have sent them, are more of a customized service that you can more than likely access as a web based service. Now there are a few email services like AOL, I believe which can allow you to unsend emails you have sent, but again most of the email client services that do offer this feature or custom and more than likely paid services as well.
There is one web-based service I do know of however, called Big String, which will allow you to send emails and then edit and I belive can expire (remove) that email once it is sent.
Here is the link the pros and cons of Big String you can review if you are interest. It is pretty good in the sense that it will allow you to certify your emails as well as edit and expire them, plus a few more features. So take a look for yourself and try it if you like after all it is free and starts provided with 2GB of storage...About BigString.com
(As explained from about.com
(Official Website- be sure to check out details about service under "Features")
So please feel free to let me know if this helps. I will be here and glad to continue to assist if you need additonal assistance or have questions regarding the information I have provided to aid you with your question
Thanks for your patience, I await your update.