mail out is blocked because of smtp server name

[brownh@hartford-hwp.com (Haines Brown)]

I have a dynamic IP address. When I tried to send a message to
postfix-users@cloud9.net, it was rejected: 

  <postfix-users@postfix.org>: 
    host mail.cloud9.net[168.100.1.4] said: 
    554 Service unavailable; 
    Client host [64.252.171.18] blocked using rbl-plus.mail-abuse.org

I went to http://mail-abuse.org/ to remove my IP address from its
abuse list. I do a MAPS lookup there and am told: 

  The IP address 64.252.171.18 does not appear on the MAPS RBL.

  However, it does appear on other lists:
  List Entry
  dul 64.252.160.0/20

  Please see the correct web pages for information about the other lists, 
  contact information, why the address is listed, and how to get it removed, 
  if applicable. Please do not contact the RBL team for RSS, DUL, or other 
  list problems.

I have no idea what "the correct web page" might be, but DUL is a link to
Mail Abuse Prevention System Dial-up User List page. I don't use
dial-up, and so don't know if my IP address in the DUL database is an
error. The page says: 
	
  If you're an end user whose mail was blocked and you referred here, please 
  read the end user information page. 

I presume I'm an "end user,"  and the "end user information page"
offers information about:   

  * If you were blocked...
  * How to start sending mail again 

It says that if I have a standard mail client (is rmail under emacs
"standard"?), my mail program is set to use a mail server other than
the one your current Internet provider provides.

However, that is not the case, and I regularly use the same mail
server name for other lists and e-mail. However, my smtp server is
provided by my web hosting service, while DSL broadband I get from my
ISP. I wonder if that results in an inconsistency in the message
envelope. The recommended fix is to set the outbound mail to my ISP's
mail server, but that is what I have.

Haines Brown