5.7.0: security or policy refusal, unspecified
The message or session was refused for a security or policy reason that the server did not describe more precisely, or chose not to reveal.
- Standard
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 5.7.0
- Provider
- Standard SMTP codes
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
5.7.0 Other or undefined security status
What it means
X.7.x is the security and policy group, and 5.7.0 is its general code. RFC 3463 says it may also be used when security policy forbids describing the condition further, so providers use it for many different refusals. Two uses are fixed in RFCs: 530 5.7.0 when the server requires authentication first (RFC 4954), or STARTTLS first (RFC 3207). The temporary form, 4.7.0, is common as well: RFC 4954 uses 454 4.7.0 for a temporary authentication failure, and large providers send 421 4.7.0 to slow senders down. With 5.7.0 the message is returned; with 4.7.0 the sending server retries.
Common causes
- A submission server that requires login (AUTH) or encryption (STARTTLS) before it accepts mail.
- A content or reputation filter that refuses the message without giving a reason.
- A temporary block or rate limit from a large provider, shown as 4.7.0.
- A temporary failure of the authentication service (454 4.7.0).
How to fix it
- 01If you send through your own provider, turn on authentication and STARTTLS (or implicit TLS) in your client or app.
- 02Read the text after the code; providers often add a reason or a link.
- 03For 4.7.0, slow down and let the queue retry.
- 04If a recipient's server refused you, check your SPF, DKIM and DMARC and your IP's blocklist status.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 530Authentication required.The server requires the client to log in, or to start TLS, before it accepts this command, which usually means before it accepts any mail.
- 454Temporary authentication or TLS failure.A login or a TLS handshake could not be completed because of a temporary problem on the server; the client should try again later without changing anything.
- 5.7.1Delivery not authorised.The receiving server refuses the message because this sender is not allowed to send to this recipient, as a result of filtering by host or by recipient.
- 421Service not available.The receiving server is closing the connection and will not take mail right now. The reply is temporary, so the sending server keeps the message and tries again later.
5.7.0 at other providers
- 552 5.7.0Blocked for a potential security issue.Gmail blocked the message because something in it, typically an attachment, looks like a security risk under its content and attachment rules.
- 503 5.7.0No identity changes permitted.Your client tried to authenticate again in an SMTP session where Gmail had already accepted a sign-in.
- 550 5.7.0Relay denied: sender not registered.Google's SMTP relay refused your mail because it comes from an IP or domain that is not registered in your Google Workspace account's relay settings.
- 550 5.7.0Relay account suspended for abuse.Google has temporarily suspended the account behind your relayed mail from sending, because it detected abuse such as spam from it.
- 550 5.7.0Email sending denied.Google refused to send this mail through its servers for your account, and its reply refers you to the SMTP relay error documentation.
- 554 5.7.0Too many unauthenticated commands.Gmail closed the session because your client sent too many commands without signing in, on a service that needs authentication.
Further reading
All 105 standard codesEvery code in the wikiPaste your own bounce