What this code means
The message was accepted for relay or delivery, but the requested priority—including a possible implied default—was not retained. The system reported a new priority instead. This is a success status, not a rejection.
Technical meaning
Code X.3.6 means that the message was accepted for relay or delivery even though the requested priority was not honored. The human-readable text after the status code contains the new priority, followed by SP (a space) and explanatory text.
Delivery status
The leading digit 2 denotes success. Code 2.3.6 reports a priority change when the message is accepted; it does not describe a temporary error, a permanent error, or a rejection.
- Class
- Success
- Retry
- Do not retry unchanged
- Suppression
- Check the full context
Retry decision
Do not retry based on code 2.3.6 alone because the message was accepted. If the workflow depends on priority, inspect the reported new priority and the full event context before making a manual decision instead of resending automatically.
Suppression decision
Do not add the address or domain to a suppression list based on code 2.3.6 alone. The code does not by itself report an invalid recipient; make a suppression decision only after checking other independent events for the message and recipient.
Common causes
- The system accepting the message applied a different priority from the one explicitly requested.
- An implied default treated as the requested priority was not retained, and the system reported a replacement value.
Diagnostic steps
- Inspect the raw SMTP response or report and confirm that the enhanced code is exactly 2.3.6 and that the reply belongs to the success class.
- Read the text after the status code: identify the new priority, the following space, and the explanatory text.
- Compare the reported new priority with the requested or implied default priority, and correlate the response with the correct transaction in the logs.
Actions by owner
Sender administrator
- Treat 2.3.6 as success and do not trigger automatic retry or suppression solely because of this code.
- Retain the requested priority, raw response, and reported new priority so the effect of the change on the sending workflow can be assessed.
Recipient administrator
- If the priority change is unexpected, inspect the receiving system configuration responsible for priority handling.
- Compare the reported new priority with the expected behavior for this transaction and share the findings with the sender administrator.
Provider
- Classify 2.3.6 as success and do not route it into automatic rejection handling.
- Retain the code, new priority, and explanatory text in the raw event so the change can be verified.
Sources and verification
The meaning, success class, and response structure were verified against the IANA registry and RFC 2034, RFC 5248, and RFC 6710 as of July 17, 2026. The retry, suppression, diagnostic, and owner-action recommendations are separate operational guidance, not standards facts or provider practice.
- iana-smtp-enhanced-status-codesT0 source
Enumerated Status Codes / X.3.6
- rfc5248T0 source
Section 2.1: registry fields and non-exclusive Associated Basic Status Code
- rfc2034T0 source
Section 4: enhanced status class agrees with SMTP reply class
- rfc6710T0 source
IANA registry reference for X.3.6
Last verified:
