Hi,
you need to add a reference to "Microsoft.Office.Interop.Outlook" to your project and then use this code:
using OutLook = Microsoft.Office.Interop.Outlook;
OutLook.Application oApp;
OutLook._NameSpace oNS;
OutLook.MAPIFolder oFolder;
oApp = new OutLook.Application();
oNS = (OutLook._NameSpace)oApp.GetNamespace("MAPI");
oFolder = oNS.GetDefaultFolder(OutLook.OlDefaultFolders.olFolderSentMail);
OutLook.Items items = oFolder.Items;
foreach (OutLook.MailItem mail in items)
{
}