550 5.7.606 Microsoft: access denied, banned sending IP
Quick answer
Microsoft rejected the connection because the sending IP is on Microsoft's own blocklist. Codes 5.7.606 to 5.7.649 all mean the IP is banned. Nothing about the recipient was evaluated.
Recommended action: Fix sender reputation
Common causes
- Spam, high complaint rates or spam trap hits from that IP.
- A shared IP at a hosting or sending provider that another customer abused.
- A compromised account or form sending from the IP.
What to do
Stop the cause, then request delisting through Microsoft's delist portal for Exchange Online, linked from the bounce message. Clean your list before you resume so the IP is not banned again.
Provider note: RocketVerifier recognises 5.7.606, 5.7.511, 5.7.708 and 5.7.750 as IP blocks on Microsoft hosts. The address comes back unknown and free, and the verification IP is cooled down automatically.
How to read 550 5.7.606
550 is the basic SMTP reply defined in RFC 5321. 5.7.606 is the enhanced status code from RFC 3463, which reads as class, subject and detail:
- Class
- 5Permanent failure
- Subject
- .7Security or policy
- Detail
- .606Microsoft: access denied, banned sending IP
Further reading
FAQ
Frequently asked questions
Are the recipients on a 5.7.606 bounce invalid?
No. Microsoft refused the sending IP before checking any recipient. Those addresses can still be valid.
Stop hard bounces before they start
Upload a list or call the API, and send only to addresses that can receive mail. Unknown results are always free.
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