How to get delisted from Microsoft 365 / Outlook.com

What this guide does and doesn’t cover

This is the public, documented removal procedure for Microsoft’s own blocked-senders list — not a guarantee of outcome or timeline. Microsoft’s own systems decide whether and when a given IP is actually removed; neither AdminKit nor any third party controls that decision. AdminKit’s blacklist check is coming soon via the AdminKit Check API; today, the fastest way to confirm you’re affected is the exact wording of the bounce (NDR) message Microsoft already sent you.

Step 1: read the exact error code in the bounce

Microsoft uses different codes for different situations, and the removal path depends entirely on which one you got, per Microsoft’s own documentation:

• 550 5.7.606 through 550 5.7.649 — “Access denied, banned sending IP.” This is a self-service case, handled through the delist portal (Step 2 below).
• 550 5.7.511 — “Access denied, banned sender.” Microsoft’s documentation states plainly that the delist portal does not apply to this code — it requires emailing Microsoft directly (Step 3 below).
• A bounce naming Outlook.com’s consumer service and referencing a separate blocklist (for example Spamhaus). If the NDR points at a third-party list rather than a Microsoft-specific code, the actual removal procedure is that list’s own — see how to get delisted from Spamhaus or how to get delisted from Barracuda depending on which one is named.

Step 2: use the delist portal for a 5.7.606-649 code

1. Go to the Office 365 Anti-Spam IP Delist Portal at sender.office.com.
2. Enter the email address that received the bounce and the IP address named in the error message — one email address and one IP per visit.
3. Submit the form. Microsoft sends a confirmation message to the email address you entered, with a link back to the portal.
4. Follow that link and select Delist IP to complete the request.

Per Microsoft’s own documentation, results can vary and it may take up to 24 hours or longer for the removal to take effect. Submitting the request doesn’t pause the block while it’s pending.

Step 3: email Microsoft directly for a 5.7.511 code

The delist portal explicitly does not handle this error. Instead, send an email to [email protected] including the full NDR text and the affected IP address. Microsoft’s documentation states it will respond within 48 hours with next steps — this is a manual review rather than a self-service form, so expect it to take longer than the portal path above.

Step 4: fix the underlying cause, or expect to be re-blocked

Microsoft’s guidance is direct about this: even after an IP is delisted, mail still has to clear its ordinary spam, spoofing and phishing filtering to be delivered, and a sender whose messages are “abusive or malicious” can be blocked again. Before (or while) requesting removal, it’s worth checking the same things that drive most mail-reputation problems generally:

• Authentication gaps. Missing or misconfigured SPF, DKIM or DMARC records are a common contributor to Microsoft’s filtering decisions — see SPF, DKIM and DMARC explained to check your domain’s current setup.
• A shared or dynamic IP. If the blocked IP is shared hosting, a VPS range, or CGNAT space, abuse from an unrelated customer on the same address can trigger a block regardless of anything you personally sent — see what is my IP and why is my IP address blacklisted for how shared addressing complicates this.
• Sending volume or pattern changes. A sudden spike in volume, a new campaign to a purchased or stale list, or a high bounce/complaint rate are all signals Microsoft’s filtering weighs — these are operational practices to review, not something a delist request alone resolves.

Ongoing monitoring: Smart Network Data Services (SNDS)

Separately from delisting, Microsoft offers Smart Network Data Services (SNDS), a free sign-up for senders to see complaint-rate and filtering data for IP ranges they’ve verified they control. It’s not a delisting tool — being enrolled in SNDS doesn’t prevent or resolve a block — but for a sender who delivers mail to Outlook.com, Hotmail or Live addresses regularly enough to care about reputation, it’s the clearest window Microsoft provides into how its systems are currently scoring those IPs, often before a block happens at all.

This guide is general information, not a security audit of your specific network — see our disclaimer for what AdminKit's guidance does and does not commit to.