Apparently an email I sent did not go through correctly and I keep getting the following message.

An unknown error has occurred.  Server: 'smtp.iprimus.com.au' Windows Live Mail Error ID: 0x8007007A Protocol: SMTP Port: 25 Secure(SSL): No   

I do not mind if this is never sent, but I want to remove it from my system. How do I remove the problem email? 

 Jeff Leaney