E-Mails to Hotmail Bounce 550 SC-001: Part of Your Network is on Our Block List

Having trouble sending e-mail to @hotmail or @live addresses? Trouble like:

Diagnostic-Code: SMTP; 550 SC-001 (BAY0-MC4-F36) Unfortunately, messages from xxx.xxx.xxx.xxx weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors.

The irony of course is that the URL provided gives you less information than the error message:

550 SC-001 Mail rejected by Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help.

Spam-like characteristics can mean anything but at least twice I've had this problem the issue was being on Hotmail's internal IP blacklist. Like it said the first time.

First, you should check to see if you're on any of the public RBLs: http://whatismyipaddress.com/blacklist-check. If you are, you have real problems and need to sort that out before bothering Microsoft. Chances are, however, you aren't - especially if we're dealing with a simple web server and not a dedicated mail server.

If you're sure you're really not spamming Hotmail fill out the Deliverability Issue Submission form at https://support.msn.com/eform.aspx?productKey=edfsmsbl2&ct=eformts. In a few hours the automated system will review your case and if successful you will receive an e-mail like this:

Dear Soey McSoandso

We have completed reviewing the IP(s) you submitted. The following table contains the results of our investigation.

The reported deliverability problem has been mitigated by the automated system. Mitigation may take 24 - 48 hours to replicate completely throughout our system. Please note that mitigating this issue does not guarantee that your email will be delivered to a user’s inbox.

Regardless of the deliverability status, Hotmail recommends that all senders join two free programs that provide visibility into the Hotmail traffic on your sending IP(s), the sending IP reputation with Hotmail and the Hotmail user complaint rates.

Junk Email Reporting program (JMRP) When a Hotmail user marks an email as "junk", senders enrolled in this program get a copy of the mail forwarded to an address of their choice. It allows you to see which mails are being marked as junk and identify mail traffic you did not intend to send. To join, please visit http://support.msn.com/eform.aspx?productKey=edfsjmrpp&page=support_home_options_form_byemail&ct=eformts.

Smart Network Data Services program (SNDS) This program allows you to monitor the 'health' and reputation of your registered IPs by providing data about traffic such as mail volume and complaint rates seen originating from your IPs. To register, please visit http://postmaster.msn.com/snds/.

There is no silver bullet to maintaining or improving good IP reputation, but these programs help you proactively manage your email eco-system to help better ensure deliverability to Hotmail users.

Thank you,

Hotmail Deliverability Support Service

If not successful, being that the system is automated you may have to go hunting for a new subnet.

Both of the tools linked above are excellent sources of information if you administrate an ISP mail server or mail servers for third parties and JMRP is especially useful for tuning mass mail marketing campaigns.


• Ryan

Thanks a lot for the post, the old Deliverability Issue Submission form link posted pretty much everywhere no longer works, I've been searching all over for a new link, and the one you posted worked.

• Leelz

Thank you very much for your helpful post. I came here right off Google as my new dedicated server's IPs were blocked by MSN. I sent them a request so it should be responded to in 24 hours.