Outlook "Resend" function creates a copy. If the mail did not go through, why do you need another copy in your "Sent Items" folder?

This Visual Basic code will resend a letter without copying it.

Sub ReSend()
Dim CurrentApplication As Application
Dim CurrentNameSpace As NameSpace
Dim OutboxInspector As Inspector
Dim CurrentMailItem As MailItem
Set CurrentApplication = CreateObject("Outlook.Application")
Set CurrentNameSpace = CurrentApplication.GetNamespace("MAPI")
Set OutboxInspector = CurrentApplication.ActiveInspector
Set CurrentMailItem = OutboxInspector.CurrentItem
CurrentMailItem.Send
End

To use, just open the letter in question and run the macro.