550 5.7.507: Microsoft 365 rejected by recipient
550 5.7.507Access denied, rejected by recipientPermanent: retrying will not helpFrom Microsoft 365 and Outlook.com
550 5.7.507 Access denied, rejected by recipient
What it means
With 5.7.507, Exchange Online is telling you that the receiving organization, not Microsoft as a whole, decided against accepting your traffic. The rejection usually reads like "Access denied, rejected by recipient" and points at your sending IP.
That makes it a local policy decision inside one tenant. Other Microsoft 365 customers and Outlook.com may still take your mail normally. Contrast this with 5.7.606, which is a Microsoft wide ban on the IP, and with 5.7.513, which is the explicit customer block list wording.
Because a person in the recipient organization made or approved the rule, only they can remove it. Microsoft support will not override a tenant’s own choice.
Likely causes
- The recipient’s admin added your IP or range to a connection filter or block list after earlier unwanted mail.
- Your mail shares an IP with another sender (for example on a shared hosting server) that the recipient blocked.
- A tenant transport rule refuses mail from your network or country.
- An earlier incident, such as a compromised account at your end, led the recipient to block you and nobody undid it.
How to fix it
- Confirm the IP named in the NDR is really yours and is your current outbound address.
- Contact the recipient by another channel and ask their IT team to check the connection filter policy and tenant allow/block list for your IP.
- If you were compromised, explain what you cleaned up so they are comfortable removing the block.
- If you send from shared hosting, ask your provider for a dedicated IP or route through a reputable relay so you do not inherit someone else’s block.
Checks that apply
- Blacklist Check If your IP is also on public DNSBLs, that probably explains why the recipient chose to block it, and you can clean those up first.
- ASN Lookup Shows who owns your sending IP range, which matters when the block was placed on a shared hosting network.
- MX Lookup Proves the recipient domain is on Exchange Online, so the rule lives in their Microsoft 365 tenant.
FAQ
- Can I use the Microsoft delist portal for 5.7.507?
- Usually not. The portal at sender.office.com removes Microsoft wide IP bans, while 5.7.507 reflects the recipient organization’s own choice.
- Does this affect all my Outlook recipients?
- No. It applies to the one organization that blocked you, which is why other Microsoft 365 domains keep accepting your mail.