today a user told us, that he can't send eMails to a valid address on our his client and the bounce message like the following:<domainname.com #5.7.1 smtp;554 5.7.1 Message cannot be accepted, rules rejection>i'm using exchange 03 and i didn't enable all the filter. Does anyone have any suggestions here? thank you

He cant send email to you, or someone in your org cant send to someone else?Either way, there is anti-spam/content filtering installed on a smtp gatgeway that is dropping the message.

he can send a email to the other in the organisation. but, he cannot send a email to few client and i saw that my ip address is listed in ips.backscatterer.org. do you have any suggestion

There is typically a place at the RBL sites where you can ask that your ip is removed. If they do not remove it, ask the recipients org to whitelist you if possible.To keep yourself off these types of lists, do recipient filtering against AD so you do not accept messages for invalid recipients.If you accept internet mail directly to your Exchange 2003 Server, you can configure recipient filtering following the instructions here:http://support.microsoft.com/kb/823866 To create a recipient filter, follow these steps: Start Exchange System Manager.Expand Global Settings, right-click Message Delivery, and then click Properties.Click the Recipient Filtering tab.To filter e-mail based on a particular e-mail address, click Add, type the e-mail address, and then click OK.To filter messages that are directed to e-mail addresses that do not exist in your organization, click to select the Filter recipients who are not in the directory check box.