Undeliverable email with #5.5.0 smtp;550 Mail rejected

[chicagotech]

We are running Exchange 2003. Since last night, all our users can't send email to hotmail.com. The following are the undeliverable message.
Your message did not reach some or all of the intended recipients.

Subject: good friday off

Sent: 3/21/2008 11:16 AM

The following recipient(s) could not be reached:

boblin@hotmail.com on 3/21/2008 11:15 AM

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.

<owa.chicagotech #5.5.0 smtp;550 OU-002 Mail rejected by Windows Live Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems. If you are not an email/network admin please contact your E-mail/Internet Service Provider for help. Email/network admins, please visit http://postmaster.live.com for email delivery information and support

- according to my experience, similar issue could occur if your Exchange
server IP address or domain name is blocked by the Hotmail email server.
This could occur if your Exchange server was open on relay and it was used
by vicious senders to send malicious emails.

To resolve the problem, it is needed to contact our Hotmail team to remove
your Exchange server from the block list. For your convenience, I listed
the following methods to contact our Hotmail team for your reference:

After contacting our Hotmail support team, it is expected to get a reply
from them. But it may take a few days to get the reply. Your patience is
greatly appreciated.

Meanwhile, please be assured I will work closely with you until the issue
is fixed. If the issue cannot be fixed by contacting our Hotmail team,
please feel free to let me know and we will further discuss it.

Methods to contact Hotmail team
=============

1] Fill a Form on the website

[http://support.msn.com/eform.aspx?productKey=edfsmsbl&page=support_home_opt
ions_form_byemail&ct=eformts]

or

[http://support.live.com/eform.aspx?productKey=wlmaildesktop&page=wlsupport_
home_options_form_byemail&ct=eformts]

Kindly Note: When accessing the link above, please make sure all the
information in the [] has been included.

2] Or you can send a mail to nocmail@microsoft.com
<mailto>
with list of answers for list of Questions.
----------------------------------------------------------------------------
--------

1. What are the IP addresses of your outbound mail servers (as seen by the
receiving server)?

2. Is your server a dedicated or shared server?

3. What ISP, operating system, mail transport software, and/or mailing list
management software are you using?

4. How are "bounce messages" (non-delivery notices) handled by your system?

5. How frequent are your mailings? What are the volumes of these mailings?

6. What are some of the accounts on Microsoft's systems that you are
attempting to send to?

7. Do your SMTP logs show any failed transactions when attempting to send
to addresses at MSN, MSN Hotmail or other MSN Services? If so, please
include them online in your response.

8. Can you telnet to port 25 of mx1.hotmail.com from your mail server(s)?

9. Can you traceroute to 216.32.183.201 from your mail server(s)?

10. Please include samples of a few of the messages you are sending, with
complete headers (as seen by your recipients.)

11. In what manner(s) are recipients added to your mailing list(s)?

12. Provide the URL of your web site.

13. Provide the URL of your Privacy Policy.

14. Provide the URL at which users opt-in to receive your mailings.

15. Provide the URL at which users may choose to permanently unsubscribe
from your
mailing list.

16. Are you currently a Return Path client? Are you Sender Score Certified?

17. Do you publish Sender Policy Framework (SPF)/Sender ID records for your
IP?

18. Do you use separate IP's for your transactional vs.
promotional/subscription marketing communications?

19. Are you in the Junk Mail Reporting Partner Program?

20. Do you use Smart Network Data Services?

[chicagotech]

After run nslookup with set type=mx command and ping, we found one of our OWA servers was pointing to our web site instead of our email server. After our ISP corrected the problem, it works. Thank you.

[fenton]

Also to troubleshoot, test hotmail.com availability by using tracert 216.32.183.201 and telnet mx1.hotmail.com 25.

[chicagotech]

Also you may want to check your IP reputation and SMTP log for the troubleshooting.

[chicagotech]

We have the same problem. After contacting live.com tech support, they answer as follow:

This block lasts up to 72 hours and then is removed. If again the large majority of all the email from the IP is marked as spam it is blocked again, and so on indefinitely. The block against your IP is set to be lifted at 9-11-2008 3:09:00 PST.