How do I unsend an e-mail message if it was sent using Outlook Express? Is it possible?

No its not possible. Unsend is a feature only with proprietary e-mail systesm and only within the system. The only e-mail system I know that has it is AOL and then you can unsend only if the recipient hasn't opened it.

There is a feature in outlook to "unsend" an email but all it does is sends a new email to the person and ask them to ignore the previous email, something you could do yourself, so it's a very useless feature.

How do I unsend an e-mail message if it was sent using Outlook Express? Is it possible?
It cannot be done other than an AOL user to another AOL user.