Permanent failure — do not retry
SMTP 550 5.7.708
traffic not accepted from this IP (Microsoft 365)
SMTP 550 5.7.708 means Microsoft 365 will not relay mail from your tenant's sending IP because that IP has a low reputation. The text reads "Access denied, traffic not accepted from this IP." Microsoft says it is most common on new or trial tenants.
How it appears
550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP.
What causes it
- The tenant is new or on a trial and has no sending history.
- Outbound mail from the tenant looked like spam.
- Mail is relayed through Microsoft 365 from an on-premises server or app with a poor-reputation IP.
How to fix it
In order — try the first one first.
- Have an admin contact Microsoft Support and ask for an exception for the IP.
- Do not send bulk or cold mail from a new tenant. Build volume gradually.
- Make sure SPF, DKIM and DMARC are set up for every domain in the tenant.
Common questions
- What does SMTP 550 5.7.708 mean?
- SMTP 550 5.7.708 means Microsoft 365 will not relay mail from your tenant's sending IP because that IP has a low reputation. The text reads "Access denied, traffic not accepted from this IP." Microsoft says it is most common on new or trial tenants.
- Should I retry a 550 5.7.708 error?
- No. 550 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 550 5.7.708?
- Have an admin contact Microsoft Support and ask for an exception for the IP.
Other 550 replies
- 550 5.1.1 — mailbox does not exist
- 550 5.7.1 — message refused by policy
- 550 5.4.1 — recipient address rejected, access denied
- 550 5.2.1 — mailbox disabled, not accepting messages
- 550 — mailbox unavailable
- 550 5.1.0 — address rejected, other address status
- 550 5.1.10 — recipient not found (Microsoft 365)
- 550 5.1.8 — bad outbound sender (Microsoft 365)
- 550 5.4.5 — daily sending limit exceeded (Gmail)
- 550 4.4.7 — message expired in the queue
- 550 5.7.25 — no PTR record for sending IP (Gmail)
- 550 5.7.26 — blocked, sender unauthenticated (Gmail)
- 550 5.7.27 — SPF authentication failed (Gmail)
- 550 5.7.28 — unusual rate of unsolicited mail (Gmail)
- 550 5.7.23 — SPF violation (Microsoft 365)
- 550 5.7.124 — sender not in allowed senders list (Microsoft 365)
- 550 5.7.509 — DMARC failed, policy reject (Microsoft 365)
- 550 5.7.606-649 — banned sending IP (Microsoft)
- 550 5.7.705 — tenant has exceeded threshold (Microsoft 365)
- 550 5.7.750 — blocked from sending from unregistered domains (Microsoft 365)
- 550 5.7.515 — authentication required for high-volume senders (Outlook.com)
- 550 5.7.1 S3140 — IP range on Outlook.com block list
Last reviewed 2026-09-11