Microsoft Blocklists

Microsoft maintains its own internal blocklists to reject emails from specific IP addresses or IP networks. Any IP address listed by Spamhaus is automatically added to Microsoft’s blocklist as well. To the best of our knowledge, Spamhaus is the only external (DNS-based) blocklist that Microsoft uses. All other IP addresses or IP networks are listed based on non-public criteria determined by Microsoft. The blocklists operated by Microsoft contain a high number of false positives, as Microsoft often lists large IP networks.

There are two separate blocklists that Microsoft uses for different platforms. One of these is used for emails sent to hotmail.com, live.com, outlook.com, and msn.com addresses, while the other blocklist is used for all emails routed to Office 365.

If you receive an error message from Microsoft when sending emails from one of our servers, please check the error message to determine which blocklist the IP address is on. Please ensure that your server is not sending spam and that your IP address is not on a DNS-based blocklist. Also, make sure your emails comply with Microsoft’s policies, procedures, and guidelines, which can be found on the following webpage: https://postmaster.live.com/pm/policies.aspx

You can then follow the instructions to remove your IP address from the blocklist.

Outlook

If an IP address is on the Outlook block list, emails from that IP address will be rejected with the following error message:

550 5.7.1 Unfortunately, messages from [x.x.x.x] weren't sent. 

Please contact your Internet service provider since part of their network is on our block list (S3140). 
You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors.

Here is the official form to have your IP addresses or IP ranges removed from the block list: http://go.microsoft.com/fwlink/?LinkID=614866&clcid

Once you have filled out the form, you will receive an automatic reply confirming receipt.

Microsoft Support will then respond within 12 hours to let you know whether the IP address has been removed from the blocklist. Microsoft refers to this as “mitigated” or “conditionally mitigated.” If the email states the status as “not qualified for mitigation,” your IP address has not been removed from the blocklist.

Please note that this email is part of an automated process by Microsoft. This decision is made by a computer. If the IP address has not been removed from the blocklist, please reply to the email and ask Microsoft for the reason and a re-evaluation. Your email will then be escalated and processed manually by a support representative. Typically, the IP address in question will then be manually removed from the blocklist.

If your request is denied and the IP address was recently assigned to you, please inform Microsoft Support of this. Microsoft will request an email confirmation or a PDF document from us. To request this confirmation from us, please contact our support team by opening a support ticket via our Customer Center and provide us with detailed information about what Microsoft requires.

In the rare cases where all of the above measures fail, we can fill out the delisting form for your IP. We do not have any special contacts at Microsoft, but their support team sometimes responds differently to a new delisting request. If this does not work, we can change the IP as a last resort.

Office 365

If the IP address is on the Office 365 block list, you will receive the following error message:

550 5.7.606 Access denied, banned sending IP [x.x.x.x]. 
To request removal from this list, please visit https://sender.office.com/ and follow the instructions. 
For more information, please go to http://go.microsoft.com/fwlink/?LinkID=526655 (AS16012609)

To have your IP address or IP ranges removed from the blocklist, please use the form linked in the error message: https://sender.office.com/

The error message also includes a link to the workflow for removing the IP from the blocklist: http://go.microsoft.com/fwlink/?LinkID=526655

If you follow these instructions, your IP address should be removed automatically.

A second error message for Office 365 was recently reported:

550 5.7.511 Access denied, banned sender[x.x.x.x]. To request removal from this 
list, please forward this message to delist@messaging.microsoft.com. For more information, 
please go to http://go.microsoft.com/fwlink/?LinkId=526653. AS(1410) 
[VE1EUR01FT060.eop-EUR01.prod.protection.outlook.com]

If you contact the email address listed, the reply will either ask you to fill out the removal form for Office 365 or to forward a recent error message:

Please ensure that you have resolved any issues generating malicious or abusive traffic from 
the IP in question and use the portal at https://sender.office.com/ 
<https://sender.office.com/> to complete the IP removal process.

Then please wait 1–2 hours for this change to propagate throughout our entire system. 
After waiting 1–2 hours, try sending the email again.

If you continue to receive Non-Delivery Receipts (NDRs) or “bounce messages” indicating 
that the IP address is still blocked by our spam filtering system, please forward one of the most 
recent and complete error messages to us, and we will investigate further.

In the rare cases where Microsoft still does not remove the IP address, you can contact our support team. To do so, please submit a support ticket via our Customer Center. Please note that we do not have any special contacts at Microsoft. We can only fill out the form to request the removal of IP addresses. If this still does not produce the desired result, we can assign a new IP address as a last resort.

Microsoft Programs

For experienced users, two free programs from Microsoft for Outlook (not for Office 365) may be helpful: Smart Network Data Services (SNDS) and the Junk Email Reporting Program (JMRP).

Please note that you cannot remove your IP from the blacklist using either SNDS or JMRP; these tools only provide the following services:

• Insight into the traffic from the sender’s IP
• The sender’s IP reputation with Microsoft and the number of user complaints.

According to Microsoft, there is no magic formula for maintaining or improving a good IP reputation, but these programs can help you optimize your email ecosystem to improve deliverability to Microsoft users.

SNDNS

This program allows you to monitor the “health” and reputation of your registered IPs. It provides data about your traffic, such as email volume and the number of user complaints. This data is only available for IPs that send more than 100 emails per day to Microsoft accounts.

To sign up, please visit: https://sendersupport.olc.protection.outlook.com/snds/

You will need to request authorization for the IP addresses you wish to access. Microsoft uses a combination of WHOIS and rDNS to determine the owner of a specific IP address. In some cases, sending an email to your own domain is sufficient to verify ownership.

Otherwise, please send a verification request to one of the following email addresses: support@creoline.com

JMRP

This is similar to a feedback loop (FBL) in that it sends you a copy of an email that the recipient has marked as “junk.” However, to prevent listwashing, the JMRP only sends a copy of about 1 out of every 1,000 emails marked as junk. This limits the usefulness of the JMRP and means that many senders receive few to no complaints via JMRP, even though recipients are actually marking their emails as junk.

You must first be authorized for the IP in the SNDS (see above) before you can create a feed for it in the JMRP.

To sign up, please visit: https://sendersupport.olc.protection.outlook.com/snds/JMRP.aspx

Please also note that, since we have access to all of our IPs in SNDS, we can create, modify, and delete JMRP feeds for our IPs. At this time, we do not have any feeds for IPs belonging to root servers.