You, personally, may not have been blacklisted, but your server may have.
The Great OZ has found "you" wanting, and has shut down your access to the internet, via e-mail...you or your sever has been acknowledged as a source of spam or malware, or nastier stuff. The server may not have any control over the issue, as it is often the result of those using the service, but it does have an obligation to track down its users who are abusing their priviledges by being the source of spam, etc..
Do some research on black lists on the net, and you will find a few progs to track down the cause of the message. And contact your server to inform them of the issue.
If sending mail is urgent...check out mail2web.com, it is fantastic...
Edited by b1caez01, 04 November 2006 - 02:43 AM.