why send mail is SPAM

im using this how to http://www.howtoforge.com/virtual-users-domains-postfix-courier-mysql-squirrelmail-ubuntu9.04

why send email to my yahoo or gmail SPAM.
how fix this?

im using no-ip to redirect mail server.

thanks in advance to of you here...

 

Please check if your server is blacklisted: http://mxtoolbox.com/blacklists.aspx

 

ok thanks i will try.