Emails disappearing from sent items

[Falcon_LS]

I'm using my Hotmail account through Outlook 2010, and there are instances where some emails randomly disappear from the sent items box. I wasn't worried about it, but I had a rather important email disappear this morning (it was sent last night). Any idea how I can resolve this and hopefully recover the email? Thanks!

 

[Triple_Se7en]

If you type "Outlook Mails Disappearing" in your Google search box, there's plenty of help there.