Problem with sent mails

When I receive an e-mail and I answer the e-mail and than I the delete the mail the mail is also deleted in the box sent mails, why is that? How can I save my deleted mails in my sent box? Thanks.

This is a feature of the conversation mode in all views. You are deleting the conversation, not the individual message.

You can disable conversations in all views in Menu > View > Conversations. That way when you click the delete button, it deletes the individual message. Or, if you want to keep the conversation mode in all views, you can right-click on the message header in the message pane, and select delete.