Microsoft 365

What they published

In their own words.

• A blocked source IP produces a bounce that names the delist portal in the bounce text itself.

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

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

• Delisting is not instant, and Microsoft declines to promise a number.

  “Results can vary widely before the restrictions are removed. It might take up to 24 hours or longer.”

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

• One address and one IP per submission.

  “Use the email address that received the NDR, and the IP address that was specified in the error message. You can enter only one email address and one IP address per visit.”

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

The numbers

Only the ones they printed themselves.

• 5,000 emails per day

  Bulk sender threshold

  Domains sending to Outlook.com, enforced from 5 May 2025

  Microsoft, Outlook.com postmaster — sender requirements · publisher states no date

The negative space

2 things everybody repeats that Microsoft 365 has never said.

An absence is harder to check than a claim, so each one links the page where you can confirm the words are not there — and where Microsoft 365 states outright that it will not publish something, that refusal is quoted.

• The delist portal handles every Microsoft block.

  It does not, and this is the single most expensive misunderstanding in the category. A 5.7.511 block cannot be cleared through the portal at all — Microsoft says so on the same page that documents the portal. People spend days resubmitting a form that was never going to work.

  “If you receive the error 5.7.511 go to the How to fix error code 5.7.511 section. You can't use the delist portal to fix yourself.”

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

• Outlook.com and Microsoft 365 are one system with one delisting form.

  They are two, with two forms. The delist portal at sender.office.com covers Microsoft 365; the consumer service has a separate support request form entirely. Filing at the wrong one produces no error and no result.

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

What you have in front of you

The literal bounce string.

• 550 5.7.606-649 Access denied, banned sending IP

  Your source IP is on the blocked senders list.

  Do this: The self-service delist portal at sender.office.com clears this one.

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

• 550 5.7.511 Access denied, banned sender

  A block that Microsoft wants to investigate before lifting. The portal is closed to you here.

  Do this: Forward the bounce to delist@microsoft.com with the full NDR code and the IP. Microsoft states it will come back within 48 hours.

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

Getting unblocked

The removal path, and whose job it is to file it.

Every delisting guide tells you where the form is. The half nobody prints is whether you can complete it: on a shared sending pool the listed address is your platform’s and the submission is theirs to make, so a marketer sent to the form arrives without the one thing it asks for.

• Office 365 Anti-Spam IP Delist Portal — self-service, one IP and one address per visit.

  sender.office.com

  Part platform, part you

  The form wants the IP from the bounce. On a shared pool that address is your sending platform's and the submission is theirs to make; on a dedicated IP it is yours.

  How long: Up to 24 hours or longer — Microsoft publishes no firm figure.

  What it asks for

  • The email address that received the bounce
  • The exact IP address named in the bounce

  The trap: Does not work for 5.7.511. Read the code in your bounce before you open the form.

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024

• 5.7.511 only: email delist@microsoft.com with the full bounce.

  Part platform, part you

  Same split as the portal — whoever owns the listed IP has to send it, and on shared infrastructure that is not you.

  How long: Microsoft states it will contact you within 48 hours with next steps.

  What it asks for

  • The full NDR code
  • The IP address from the bounce

  Microsoft Learn, Remove yourself from the blocked senders list and address 5.7.511 Access denied errors · 10 Jun 2024