[yigithan]

To avoid accidentally sending an email in Outlook, I once learned a useful trick: add a nonexistent email address, like sdfsdf to the To or CC field. Email would not be sent until you removed it. Lo and behold, one day I entered sdfsdfsdf, and it resolved. Someone of course was using this as a test group name.

[zaik]

Why not simply leave To and CC empty until it's ready to send?

[yigithan]

Right, for new email leaving them empty would work. This is for when you reply to a thread.