550 5.7.505: Microsoft banned recipient
550 5.7.505Access denied, banned recipientPermanent: retrying will not helpFrom Microsoft 365 and Outlook.com
550 5.7.505 Access denied, banned recipient
What it means
Exchange Online uses 5.7.505 when the destination mailbox itself has been banned by Microsoft and is no longer allowed to receive. The problem sits on the recipient side: nothing about your domain, IP, or content caused it.
Compare it with 5.1.1 or 5.1.10, where the address simply does not exist, and with 5.2.2, where the mailbox exists but is full. A 5.7.505 recipient may well exist in the directory, but Microsoft has blocked delivery to it, usually because the account was involved in abuse or is being investigated.
It is permanent. Sending again, from another IP or with a different subject, will produce the same bounce until the recipient’s organization sorts it out with Microsoft.
Likely causes
- The recipient account was used for abuse and Microsoft blocked it from receiving as well as sending.
- The recipient tenant is under a Microsoft enforcement action and selected mailboxes were restricted.
- The mailbox is a target of repeated abuse and was locked as a protective measure.
How to fix it
- As the sender, stop retrying and reach the person another way (phone, a different address, or their colleagues).
- Tell the recipient’s IT team the exact address and the full NDR text, including the date and time.
- As the recipient’s admin, check the account’s status in the Microsoft 365 admin center and Defender portal, and open a support case with Microsoft if the block is not visible to you.
- Once Microsoft confirms the recipient is restored, send one test message before resuming normal mail.
Checks that apply
- MX Lookup Confirms the recipient domain really routes to Exchange Online, so you know this NDR is a Microsoft decision and not another gateway.
- Email Header Analyzer Reading the NDR headers shows which Microsoft server generated the bounce and the exact time to quote to support.
FAQ
- Is a 5.7.505 bounce my fault as the sender?
- No. The ban applies to the recipient address, so the fix is on the receiving organization’s side.
- Should I remove the address from my mailing list?
- If it keeps bouncing with 5.7.505 for more than a few days, yes. Repeated sends to banned recipients add nothing and can count against your list hygiene.