Hi there,
I am also having the problem with outgoing e-mails for which I am getting the blacklist message.
I'm using Windows Live Mail 2012 and the message is:
An unknown error has occurred.
Subject 'hello'
Server Error: 421
Server Response: 421 csmtp1.tb.ukmail.iss.as9143.net cmsmtp Sorry your IP [deleted] is active in our local abuse blacklist. Contact Virgin Media abusedesk for delisting requests.
Server: 'smtp.blueyonder.co.uk'
Windows Live Mail Error ID: 0x800CCC67
Protocol: SMTP
Port: 25
Secure(SSL): No
[MOD EDIT: Personal and private information has been removed from this post.]