Microsoft mail servers 550 5.7.606.649.blocklist
Reputation or policy
Reputation or policy means the receiving provider rejected the message for a provider-specific reason. Use the diagnostic text before deciding on retries or suppression.
Decision
Do not retry unchanged. Fix the sender setup first.
Confidence: medium. Recipient validity: unknown.
Match this reply
- SMTP stage
- Connection
- Endpoint
- Inbound MX
Access deniedbanned sending IPblockedStart here
- 1
Pause or slow sending to that provider while you review complaint rate, bounce rate, and recent volume changes.
- 2
Check SPF, DKIM, DMARC alignment and make sure the message is expected by recipients.
Confirm the cause
- Review recent sending volume, bounce rate, complaint rate, and list hygiene for this provider.
- Confirm SPF, DKIM, and DMARC alignment so reputation problems are not made worse by authentication failures.
- Resume with lower provider-specific volume only after deferrals stop or the provider accepts test mail.
App handling
- Treat this as a sender setup incident, not a bad recipient.
- Hold similar mail for the same sender domain or provider until the fix is verified.
- Retry after a fresh single-recipient test succeeds.
Avoid
- Do not retry unchanged in a loop.
- Do not suppress the recipient unless the text explicitly says the mailbox is invalid.
- Do not treat a permanent SMTP code as proof that the address is bad; policy and routing failures can also be permanent.
Common causes
- Volume increased faster than the provider trusts for this sender.
- Recent bounces, complaints, or low engagement damaged sender reputation.
- The provider applied a traffic, content, or sender policy to protect recipients.
Developer details
Fields to log
raw SMTP replyremote MX or hostSMTP stagereply codeenhanced codeprovidermatched rule idrecipientsending domaindecisiontimestampprovider retry countsend volume windowbounce rate
Classifier evidence
- Specific cause
- microsoft ip blocklist
- Evidence
- official+observed