550 5.7.708: traffic not accepted from this IP

What it means

Microsoft's description of 5.7.708 is short: the message was sent from an IP address with a low reputation, and the problem is more likely to affect new customers, such as those on a Microsoft 365 trial. Its error table groups the code with 5.7.705, where most of a tenant's traffic is detected as suspicious and its sending is banned, and tells admins to resolve any compromise or open relay before contacting support. For a trial tenant, Microsoft says to ask support for an IP address exception until Exchange Online licenses are assigned.

Common causes

• The sending IP has a low reputation with Microsoft.
• The tenant is new or on a trial and has little sending history.
• Compromised accounts or an open relay sent suspicious traffic.

How to fix it

1. 01Admins on a trial: contact Microsoft Support and ask for an IP address exception until you assign Exchange Online licenses.
2. 02Check for and close any compromise or open relay that could have hurt the IP's reputation.
3. 03Then contact Microsoft Support through your regular channel to have the block reviewed.

Sources

What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.

• Fix NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750learn.microsoft.com
• Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com

Further reading

• 550 5.7.708 Access denied, decoded
• The standard meaning of 550: mailbox unavailable