Cannot send email in Windows Live due to following message:

An unknown error has occurred.

Subject 'Fw: Your Direct Loan'
Server Error: 550
Server Response: 550 5.2.0 9VPB1m00H1lJZQp05VPBBs Message identified as SPAM - Please visit http://www.charter.com/postmaster E5110
Server: 'SMTP.charter.net'
Windows Live Mail Error ID: 0x800CCC69
Protocol: SMTP
Port: 25
Secure(SSL): No

What can I do to correct this?

Thanks.

Original title: Cannot send email in Windows Live Mail in Windows 8