550 5.7.708: access denied, traffic not accepted from this IP
Microsoft 365 blocked outbound mail from your organization because it was sent from an IP address with a low reputation. It's most common for new and trial tenants.
5.7.708 Access denied, traffic not accepted from this IP.
The full NDR text, as given in Microsoft's article on 5.7.703, 5.7.705, 5.7.708 and 5.7.750.
What 550 5.7.708 means
Microsoft documents 550 5.7.708 as an NDR generated when you send a message from an IP address with a low reputation. It says the issue is more likely to affect new customers, such as those with a Microsoft 365 trial subscription. The NDR goes to your own users: it's Microsoft 365 refusing to send your outbound mail, not the recipient refusing it.
Microsoft's fix is short. Only an email admin can fix it, and if you get this error during a trial subscription, contact Microsoft Support to request an IP address exception until you assign Exchange Online licenses.
The neighboring codes in the same article are worth knowing. 5.7.705, "Access denied, tenant has exceeded threshold", means your organization sent too much spam or bulk mail, often through a compromised server or admin account. 5.7.750 means too much mail was sent from domains that aren't accepted domains in your tenant. Microsoft's overview groups 5.7.705 and 5.7.708 together: most of the tenant's traffic was detected as suspicious, and sending was banned.
Likely causes
- Sending from a new or trial Microsoft 365 tenant with no reputation yet.
- Outbound traffic from the tenant that Microsoft considers suspicious.
- A compromised account or connector sending spam through the tenant.
How to fix it
If you sent the message
- During a trial: contact Microsoft Support and ask for an IP address exception until you assign Exchange Online licenses.
- Check for compromised accounts, unknown connectors and open relays, and fix them before asking for the block to be lifted.
- Add and verify every domain you send from as an accepted domain.
If you're the recipient or their admin
- No action needed: the block is in the sender's Microsoft 365 tenant.
Frequently asked questions
Can a regular user fix 550 5.7.708?
No. Microsoft says only an email admin in your organization can fix it. Forward the NDR to your admin.
Does 5.7.708 mean my domain is blacklisted?
Not on a public blocklist. It's Microsoft 365 refusing to send from an IP it considers low reputation, usually because the tenant is new or its traffic looked suspicious.
Sources
- Fix NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750 (Microsoft Learn)
- Email nondelivery reports (NDRs) and SMTP errors in Exchange Online (Microsoft Learn)
Provider messages are quoted as the provider publishes them. Servers can change their wording, so the bounce you received may differ slightly.
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