Hello everyone May I ask for some help on this? I have hard time send email to some domain and keep getting this message back. The message cannot be delivered due to a configuration error on the server. Please contact your Administrator. < mail1.telecel.com.py #5.3.0 X-Unix; 73> I have checked to see if we are on spam list and we are not. Reverse dns is fully set and also I have checked to see if I can telnet to server on port 25. Looks like my isp is blocking telnet since I can't even telnet to my own mail server although I know that is working. I looked on Google with no luck on this. Is this my side error or UNIX side error? Would someone telnet to this address and see if it is alive, also any help to solve this issue is greatly appreciated. Exchange 2003 with sp1 on server 2003 using xp sp2 with outlook 2003 sp1 Attention: This message, including any attachment(s), is intended only for the use of the individual(s) to which it is addressed and may contain information that is privileged or confidential. Any other distribution, copying or disclosure is strictly prohibited. If you are not the intended recipient or have received this message in error, please notify us immediately by reply e-mail and permanently delete this message including any attachment(s), without reading it or making a copy. Any outgoing message has been scanned for possible harmful file(s) or script(s), but it is your sole responsibility to run detection tools as we won't guarantee the safety of message(s).