5.7.513 Microsoft bounce: recipient custom blocklist
What 5.7.513 means
The recipient's domain added your sending IP address to its own custom block list, so it refuses mail from you.
Message text
Service unavailable, Client host [sending IP] blocked by [recipient domain] using Customer Block list
Common causes of 5.7.513
- Recipient domain has blocked your sending IP address in its custom block list
How to fix 5.7.513
- Check your sending IP with blocklist check to confirm the block.
- Ask the recipient to remove the IP from their custom block list if it was added in error.
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How to read 5.7.513
The second part, 5.7.513, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 5 is a Permanent failure (5xx): the command was rejected and the sender should not repeat it unchanged (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 7 is security or policy: authentication, authorization or policy refused the message. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.
Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.
Official source: learn.microsoft.com. Last verified 2026-10-20.
Related guides
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
- How to set up a DMARC record, from p=none to p=reject
Related codes
- 5.7.0 SMTP: security status
- 5.7.1 SMTP: delivery not authorized
- 5.7.23 SMTP: SPF validation failed
- 5.7.25 SMTP: reverse DNS failed
- 5.7.26 SMTP: authentication failed
- 5.7.27 SMTP: sender has null MX
FAQ
What does 5.7.513 mean?
The recipient's domain added your sending IP address to its own custom block list, so it refuses mail from you. This is a permanent failure.
How do I fix 5.7.513?
Check your sending IP with blocklist check to confirm the block. Ask the recipient to remove the IP from their custom block list if it was added in error.
Is 5.7.513 permanent, and should I retry?
5.7.513 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.