E-mail message stuck in Outbox.

I use Windows Live Mail. My Google Mail account also appears on my Live Mail screen. I have written an e-mail that I was intending to send from my Live Mail. I have pressed "send". For some reason the e-mail has appeared in my outbox, and is sticking there without going away, and I get a message: "An unknown error has occurred.  Subject 'Re: hello' Server: 'smtp.googlemail.com' Windows Live Mail Error ID: 0x800CCC0B Protocol: SMTP Port: 465 Secure(SSL): Yes". What is going on, and how can I send this message off??? The message is short, has no attachment. I could re-write it, but then it would look as a fresh e-mail, and it would loose its now 3 days old sending date. This I would like to avoid. Other e-mails have gone since. Thanx for your help, Andrew.