Microsoft (Outlook.com and Microsoft 365) · permanent error
5.7.508: IPv6 range sending too fast
The sender's IPv6 range sent too many messages in too short a time, so Microsoft 365 refused further mail from it.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 5.7.508
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
5.7.508 Access denied, [$SenderIPAddress] has exceeded permitted limits within $range range
What it means
Microsoft 365 applies sending limits to IPv6 ranges. 5.7.508 means the IPv6 range the sending address belongs to tried to send too many messages in too short a period, and Microsoft 365 is refusing more from it. Microsoft gives no further steps for this code. The practical answer is to slow down: lower the sending rate to Microsoft 365, spread volume over time, and find out whether other senders share the range.
Common causes
- Servers in your IPv6 range sent a burst of messages to Microsoft 365.
- Several senders share the same IPv6 range.
How to fix it
- 01Reduce your sending rate to Microsoft 365 and spread volume over a longer period.
- 02Retry later rather than resending immediately.
- 03If the range is shared, ask your provider who else is sending from it.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
Related codes
- 5.7.510Recipient domain does not accept IPv6 mail.You sent over IPv6 to a Microsoft 365 domain whose tenant has not opted in to receiving anonymous mail over IPv6.
- 5.7.25IPv6 sender without reverse DNS.Microsoft 365 refused mail from an IPv6 address that has no reverse DNS (PTR) record; the same rule also appears as 450 4.7.25.
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