How to Get Delisted by Microsoft (Outlook.com and Microsoft 365)

To get delisted by Microsoft, first work out which Microsoft blocked you. Outlook.com (Hotmail, Live, MSN) uses bounce codes like S3150 and S3140, and removal goes through the Outlook.com sender support form. Microsoft 365 uses codes 5.7.606 through 5.7.649, which you clear yourself at sender.office.com, or 5.7.511, which you email to delist@microsoft.com. Fix whatever caused the block before you ask, or the answer will be no.

Match the bounce to the process

Everything depends on the code in the bounce. Pull the full SMTP response from your ESP or mail server logs and find it in this table.

The last two rows matter because people waste time filing tickets for them. Authentication errors like 550 5.7.515 are evaluated on every message: fix your records and the next message passes. Temporary codes start with a 4, which means the receiving server is asking your server to try again later.

Before you request removal

Microsoft reviews the IP, not your explanation. If the traffic that caused the block is still flowing, the request fails, or the block returns within days. Before you file anything:

1. Find the cause. Check for compromised mailboxes or servers, sudden volume jumps, sends to old or bought lists, and complaint spikes. If you're unsure, why Outlook is blocking your emails walks through the usual suspects.
2. Stop it. Reset compromised credentials, close abused forms, pause the questionable list.
3. Check the basics. Reverse DNS (a PTR record) on the sending IP, plus SPF, DKIM and DMARC passing for your domain. The email checker covers the DNS side in one pass.
4. Confirm you own the IP. On an ESP's shared IP, the ESP files the request. Send them your bounces and let them handle it.

Delisting from Outlook.com (S3150, S3140)

1. Set up SNDS and JMRP. Register your IPs with Smart Network Data Services and the Junk Mail Reporting Program at the Outlook.com postmaster site. SNDS shows Microsoft's view of your traffic, and JMRP forwards you messages users mark as junk. Microsoft recommends both in its replies to delisting requests, so join before you ask.
2. Open the sender support form. Microsoft's documentation links the Outlook.com delisting form. You'll need to sign in with a Microsoft account.
3. Give them what they need. The blocked IP or IPs, the full bounce text with timestamps, your sending domain, roughly how much you send to Microsoft consumer addresses, how your recipients signed up, and what you've fixed. Keep it factual.
4. Watch for the reply. You'll get a ticket number and then a decision. One documented response is "Not qualified for mitigation," which means Microsoft reviewed the IP and isn't removing the block. Keep improving and reply to the ticket with what has changed since.

For the full background on these codes, see Outlook.com S3150 / S3140.

Delisting from Microsoft 365 (5.7.606 to 5.7.649)

Microsoft documents the bounce like this (a real one shows a single code in the range, such as 5.7.606):

550 5.7.606-649 Access denied, banned sending IP [203.0.113.7]: To request
removal from this list please visit https://sender.office.com/ and follow
the directions.

The steps, per Microsoft's documentation:

1. Go to the Office 365 Anti-Spam IP Delist Portal at sender.office.com.
2. Enter the email address that received the bounce (NDR) and the IP address from the error. You can only enter one email address and one IP per visit.
3. Select Submit.
4. Microsoft emails a confirmation link to that address. Open it to return to the portal.
5. Select Delist IP.

Microsoft says results vary and removal "might take up to 24 hours or longer." Once removed, your mail still has to pass Microsoft 365's normal filtering, and if the IP keeps sending abusive mail, it gets blocked again.

Delisting from Microsoft 365 (5.7.511)

A 5.7.511 Access denied, banned sender bounce can't be cleared in the portal. Microsoft's instructions are to email delist@microsoft.com with the full bounce code and the IP address. Microsoft says it will contact you within 48 hours with next steps.

How to confirm you're delisted

Send test messages from the affected IP to addresses at the blocked provider and look for 250 accepted responses in your logs. Then check where they land: a freshly delisted IP often goes to Junk until it builds history, which is a separate problem covered in why emails go to junk in Outlook and Hotmail. The header analyzer will show you authentication results on the delivered copies.

How to stay delisted

• Warm the IP back up gradually, starting with your most engaged recipients.
• Read JMRP complaints and SNDS data every week.
• Remove bounces and long-term non-responders on a schedule.
• Monitor outbound volume so a compromise is caught quickly.

If the block came from a public blocklist rather than Microsoft, the process is different; the blocklist playbook and Spamhaus removal guide cover that.

When to get help

If you've filed the right request, fixed what you can find and Microsoft still won't lift the block, the cause is usually in data you haven't looked at yet. That's a good point to talk to someone who does this regularly.

FAQ

Does Microsoft charge for delisting?

No. The Outlook.com form, the sender.office.com portal and delist@microsoft.com are all free. Treat anyone offering paid "Microsoft delisting" with suspicion.

How long does Microsoft delisting take?

For Microsoft 365's portal, Microsoft says up to 24 hours or longer, and for 5.7.511 it promises contact within 48 hours. Outlook.com doesn't publish a timeline.

Can I delist more than one IP at a time?

Not in the Microsoft 365 portal: it takes one IP and one email address per visit. Outlook.com requests can cover more than one IP; Microsoft's replies list each IP it reviewed.

I was delisted but I'm still bouncing. Why?

Check the code again. You may have a second block (for example, Outlook.com and Microsoft 365 at the same time), a different IP in the pool, or an authentication error that delisting can't fix.