Microsoft Blacklists

Microsoft uses and maintains its own blocklists to filter emails by IP address. As far as we know, the only external database used to create these blocklists is Spamhaus.

Microsoft uses two blocklists: one for Outlook, Hotmail, Live, and MSN, and another for Office 365.

If you receive an error message from Microsoft:

Find information in the message about which blocklist the sender's address is on.
Verify that your server is not sending spam.
Confirm that your server's IP address does not appear on any blacklists.
- You can check whether your server's (or website's) IP address is blacklisted and whether it's sending spam using specialized online services that scan hundreds of spammer and malware databases (MxToolbox Blacklist Check, DNS Checker - IP Blacklist Checker, 2ip.ru).
- The check results (for example, in MxToolbox) usually contain links to blacklist websites. There, find the IP deletion form (delist request).
- If you need help checking your server's IP address, please contact technical support by creating a ticket.
Ensure that emails sent from your server comply with Microsoft's policies and guidelines, including authentication requirements such as SPF, DKIM, and DMARC, and that these are configured correctly. Starting in May 2025, these requirements will be mandatory for senders sending more than 5,000 emails per day.
Proceed to remove your server's IP address from the blocklist.

Removing from the Outlook, Hotmail, Live, and MSN Block List

If your server's IP address is on Microsoft's first block list, you will receive an error message similar to this:

550 5.7.1 Unfortunately, messages from [1.2.3.4] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140).

Fill out the form on the Microsoft website with the following information:
- Problem description title — for example, "error sending to http://outlook.com/."
- Contact name — your name.
- Recipient domain — select one of the following: outlook.com, hotmail.com, live.com, MSN | Personalized News, Top Headlines, Live Updates, and more.
- Contact email address — enter a valid email address; replies will be sent to this address.
- Sender domain — enter the domain from which emails are sent.
- Company description — select the appropriate option (university, company, etc.).
- Outgoing IP addresses or ranges — separate with semicolons, for example: xxx.xxx.xxxxxx; yyy.yyy.yyy.yyy or xxx.xxx.xxx.xxx/28; yyy.yyy.yyy.yyy/28.
- Server type — dedicated or shared, select from the list.
- Error messages — copy and paste the full error text.
You will receive an automatic response within 12 hours. There are two possible options:
- Mitigated — the IP address has been removed from the block list.
- Conditionally mitigated — the IP address has not been removed from the block list.
If the address has not been removed, reply to the email and request additional information about the reason for the block.
The first time you contact us, you will receive a response from a bot. If you reply to it, your request will be reviewed by a live employee, who will typically remove the address manually.
The employee may refuse. The response in this case will look something like this:

"Dear sender, We have completed our review of the IP addresses you provided. Results: Not eligible for delisting 1.2.3.0/24. Our investigation has determined that the above IP addresses are not eligible for delisting. Please ensure your emails comply with Outlook.com policies and guidelines."

In this case, reply to the email requesting a more thorough investigation and explaining that your emails fully comply with Microsoft's guidelines.
In a few hours, you will receive a message stating that your request has been accepted and is being monitored. Be sure to respond — for example, "Thank you, awaiting results."
Continue the correspondence until you receive confirmation that the delisting has been removed. Save your entire message history — Microsoft may re-add the address to the block list without warning, and your message history will help expedite the delisting process.
If an employee refuses to delist a recently assigned IP address, ask the hosting company to confirm its date of issue. Notify a Microsoft representative. A request will be sent to the hosting company.
If the address is still not removed from the blocklist after the hosting company confirms, change the IP address. To do this, contact technical support.

Removing from the Office 365 Blocklist

If your server's IP address is on Microsoft's second blocklist, you will receive an error message similar to this:

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/

Option 1

Go to the delisting portal: Delist IP - Delist IP
Enter the email address where the NDR was sent and the blocked IP address. You can only enter one address and one IP address per visit.
Click Submit. A confirmation email will be sent to the specified address; follow the link in it.
On the page that opens, click Delist IP.

After the block is lifted, the changes will take effect within 24 hours.

Option 2

If the error message contains code 5.7.511, you cannot use the sender.office.com portal. Forward the NDR message to [email protected].

There are two possible responses:

Option A

You will be sent a link to the form. Once completed, the address will be removed from the block list.

Option B

You will be informed that the address is not on the block list. In this case, forward the most recent error message to the same address.

If you are sure that your server is not sending spam, but the steps described above have not yielded results, please contact technical support.

Microsoft Email Monitoring Software

Microsoft offers free sender reputation monitoring tools: SNDS and JMRP. These do not remove addresses from blocklists, but help monitor and analyze email traffic to improve deliverability for Outlook, Hotmail, Live, and MSN users.

IMPORTANT:

Microsoft will conduct significant updates to both tools in 2025–2026. If you have previously used SNDS and JMRP, please ensure your settings are up to date.

SNDS (Smart Network Data Services)

SNDS provides traffic data and the number of complaints about emails sent from your server's IP address. Data is only displayed if more than 100 emails are sent from an IP address to Microsoft addresses (Outlook, Hotmail, Live, MSN) per day. Microsoft 365 / Exchange Online corporate mailboxes are not included in these statistics.

To use SNDS, you must:

Log in to the Smart Network Data Services portal using your Microsoft account.
Request authorization for the IP addresses you want to monitor. Microsoft checks the owner by emailing the standard domain contacts (abuse@ or postmaster@).

Current changes (2025–2026):

SNDS is moving to a new URL – stay tuned for official announcements on the service page.
Automatic report links now expire after 30 days. If you use static URLs in scripts or dashboards, update them.
Starting in November 2025, authentication will be required to manage network access in SNDS.

JMRP (Junk Mail Reporting Program)

JMRP lets you identify which of your emails are receiving negative ratings from recipients. Microsoft sends copies of emails that recipients have marked as spam.

To use JMRP, IP addresses must be pre-registered in SNDS. JMRP is configured through the SNDS interface.