Email in outbox I am unable to delete

I was writing an email earlier when my machine crashed. The email I was
writing is now in my outbox. However, when I try and access it, I get the
message "Message could not be displayed
Windows Mail encountered an unexpected problem while displaying this
message. Check your computer for low memory or low disk space and try again."
I have tried deleting this message, but I get a dialogue box with "Unknown
error". I've been into the Local folders into Outbox and this email is not

Unfortunately, this means that I now can't send any emails until I have
cleared this rogue one. Can anyone help, please?