Responses Sorted by Message
Last updated March 2020
| SMTP Code | Enhanced Code | Message | Comment |
|---|---|---|---|
| 550 | 5.7.1 | 550 [internal] [oob] | bounce_logger module |
| 550 | 5.6.0 | Body line too long (see RFC2822 section 3.5) | See message. |
| 503 | 5.5.1 | DATA without MAIL FROM | See message. |
| 503 | 5.5.1 | DATA without RCPT TO | See message. |
| 550 | 5.6.0 | Header line too long (see RFC2822 section 3.5) | See message. |
| 550 | 5.6.0 | Header not terminated by CR LF (see RFC2822 section 2.2) | See message. |
| 550 | 5.6.0 | Invalid header found (see RFC2822 section 3.6) | See message. |
| 550 | 5.6.0 | Lone CR or LF in body (see RFC2822 section 2.3) | See message. |
| 550 | 5.6.0 | Lone CR or LF in headers (see RFC2822 section 2.2) | See message. |
| 501 | 5.5.1 | MAIL FROM already established | See message. |
| 501 | 5.5.2 | MAIL FROM syntax error | See message. |
| 501 | 5.5.2 | MAIL FROM syntax error | Triggered by an invalid address |
| 550 | 5.6.0 | Missing CR LF . CR LF | See message. |
| 550 | 5.6.0 | Missing required RFC2822 Date field (see RFC2822 section 3.6) | See message. |
| 554 | No Valid Domain | See message. | |
| 501 | 5.5.2 | RCPT TO syntax error | See message. |
| 501 | 5.5.2 | RCPT TO syntax error | Triggered by an invalid address |
| 503 | RCPT TO without MAIL FROM | See message. | |
| 550 | 5.5.1 | RFC2821 HELO/EHLO needed | See message. |
| 550 | 5.6.0 | Required headers not found (see RFC2822 section 3.6) | See message. |
| 4.3.0 | Resource limitations, please try later | See message. | |
| 421 | 4.4.5 | Service unavailable | System outage |
| 452 | 4.5.3 | Service unavailable, batch limit reached | See message. |
| 421 | 4.4.5 | Service unavailable, concurrency limit reached | System outage |
| 452 | 4.5.3 | Service unavailable, recipients per connection limit reached | See message. |
| 452 | 4.5.3 | Service unavailable, recipients per message limit reached | See message. |
| 501 | 5.5.4 | Syntax error (no parameters allowed) | See message. |
| 421 | This message is being 421'd | Service is unavailable | |
| 554 | 5.7.0 | [internal] Blackholed | "Blackhole" option is set to "internal" |
| 450 | 4.4.1 | [internal] Connection Timed Out | See message. |
| 554 | 5.4.5 | [internal] Delivery not attempted (message expired) | See message. |
| 554 | 5.4.4 | [internal] Domain Lookup Failed | See message. |
| 451 | 4.4.2 | [internal] MAIL FROM argument hook failed | See message. |
| 451 | 4.4.2 | [internal] MAIL FROM arguments too long | See message. |
| 554 | 5.7.0 | [internal] Message manually purged | Purged messages from the system console |
| 5.7.0 | [internal] Message manually purged | Used console command, "fail domain name" | |
| 550 | 5.4.4 | [internal] NULL MX domain does not accept mail | See message. |
| 451 | 4.4.1 | [internal] No valid hosts | See message. |
| 451 | 4.4.1 | [internal] No valid hosts (unable to make any connections) | See message. |
| 551 | 5.4.6 | [internal] Private/Loopback Address | See message. |
| 451 | 4.4.2 | [internal] RCPT TO argument hook failed | See message. |
| 451 | 4.4.2 | [internal] RCPT TO arguments too long | See message. |
| 4.7.5 | [internal] SSL cert common name does not match host | See message. | |
| 4.7.5 | [internal] SSL cert must be signed by a valid CA | See message. | |
| 4.7.5 | [internal] SSL certificate subject does not match host | See message. | |
| 451 | 4.7.6 | [internal] STARTTLS required but not advertised | See message. |
| 451 | 4.7.5 | [internal] TLS negotiation failed | See message. |
| 451 | 4.4.2 | [internal] XCLIENT argument hook failed | See message. |
| 451 | 4.7.6 | [internal] XCLIENT required but not advertised | See message. |
| 451 | 4.7.6 | [internal] XCLUSTERMETADATA required but not advertised | Cluster-related error |
| 451 | 4.7.6 | [internal] XCLUSTERMETADATA supported version not advertised | Cluster-related error |
| 451 | 4.4.2 | [internal] connection closed by remote host | See message. |
| 550 | 5.7.1 | [internal] discarded by policy | See message. |
| 554 | 5.4.7 | [internal] exceeded max retries without delivery | See message. |
| 554 | 5.4.7 | [internal] exceeded max time without delivery | See message. |
| 451 | [internal] memory shortage while determining tls parameters | See message. | |
| 550 | 5.3.0 | [internal] message body missing | See message. |
| 451 | 4.4.2 | [internal] no BODY response | See message. |
| 451 | 4.4.2 | [internal] no DATA response | See message. |
| 451 | 4.4.2 | [internal] no HELO/EHLO response | See message. |
| 451 | 4.4.2 | [internal] no MAIL FROM response | See message. |
| 451 | 4.4.2 | [internal] no METADATA reponse | Cluster-related error |
| 454 | 4.4.4 | [internal] no MX or A for domain | See message. |
| 421 | 4.4.0 | [internal] no MXs for this domain could be reached at this time | See message. |
| 451 | 4.4.2 | [internal] no RCPT TO response | See message. |
| 451 | 4.4.2 | [internal] no RSET response | See message. |
| 451 | 4.4.2 | [internal] no XCLIENT response | See message. |
| 451 | 4.4.2 | [internal] no banner | See message. |
| 451 | 4.7.5 | [internal] no clustermetadata go-ahead | Cluster-related error |
| 451 | 4.7.5 | [internal] no tls go-ahead | See message. |
| 550 | 5.7.1 | [internal] processed as FBL message, and disposition is blackhole | FBL module |
| 5.7.0 | [internal] rejected by policy | See message. | |
| 4.7.5 | [internal] remote node SSL certificate not signed by a valid CA | See message. | |
| 451 | 4.4.2 | [internal] send BODY failed | See message. |
| 451 | 4.4.2 | [internal] send DATA failed | See message. |
| 451 | 4.4.2 | [internal] send HELO/EHLO failed | See message. |
| 451 | 4.4.2 | [internal] send MAIL FROM failed | See message. |
| 451 | 4.4.2 | [internal] send RCPT TO failed | See message. |
| 451 | 4.4.2 | [internal] send RSET failed | See message. |
| 451 | 4.7.5 | [internal] send STARTTLS failed | See message. |
| 451 | 4.4.2 | [internal] send XCLIENT failed | See message. |
| 451 | 4.7.5 | [internal] send XCLUSTERMETADATA failed | Cluster-related error |
| 451 | 4.4.2 | [internal] send key failed | Cluster-related error |
| 451 | 4.4.2 | [internal] send metadata failed | Cluster-related error |
| 451 | 4.4.2 | [internal] send metadatadicts failed | Cluster-related error |
| 421 | 4.3.4 | allocated resources exceeded | System outage |
| 503 | 5.5.1 | bad sequence of commands | See message. |
| 454 | certificate expired | SSL related | |
| 454 | certificate not yet valid: possible clock skew | SSL related | |
| 4.3.5 | configuration error, please try later | See message. | |
| 5.5.0 | error while reading body | See message. | |
| 501 | 5.5.2 | invalid EHLO | See message. |
| 501 | 5.5.2 | invalid HELO | See message. |
| 501 | 5.5.4 | invalid arguments to RSET | See message. |
| 421 | 4.3.0 | message is too large to process at this time | See message. |
| 4.3.5 | message not yet parsed, can't reparse | See message. | |
| 4.3.5 | message parse and assemble didn't round-trip | See message. | |
| 552 | 5.3.4 | message size limit exceeded | See message. |
| 551 | 5.7.1 | recipient blackholed | See message. |
| 550 | 5.7.1 | relaying denied | See message. |
| 451 | 4.3.0 | transaction failed | See message. |
| 501 | 5.5.4 | unexpected argument to DATA | See message. |
| 501 | 5.5.4 | unexpected command | See message. |
| 500 | 5.5.2 | unrecognized command | See message. |
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