Problem in sending e-mails to custemers

We can not send e-mails via DH mail server to our customers who have e-mail servers like and It returns error message as below. is DH mail server IP on black list? Any suggestion and solution? Thanks in advance. host [] said: 550 SC-004 (COL0-MC2-F27) Unfortunately, messages from weren’t sent. We recommend that you contact your Internet service provider. The problem is that too many unwanted messages have been sent from the following IP address above. You can also refer your provider to (in reply to MAIL
FROM command) doesn’t refer to a dreamhost mail server, but does refer to a dreamhost apache webserver instance.

If you are on shared hosting this could be the result of another customers actions.

You will need to open a ticket via support so they can help figure out if the blacklist is due to your actions or another customers.

Thank you for reply LakeRat,
I use this php script in order to send mail.
mail($email, $subject, stripslashes($body), $header)
As I understand, DH Webserver’s IP is on blacklist. So what should I do to use DH mail server or external mail server? I already opened support ticket but no reply for 5 days. Regards…