Error text MTA options

The  options specify error text describing various error conditions; see the  Table of   MTA options   for details. Not all of the error responses potentially emitted by the MTA are configurable. In general, only error conditions that can be considered more or less local, or more or less  proprietary to the MTA, such as invalid address conditions, user status  problems such as a user being disabled or   over-quota, attempts to  exceed local message size limits, Sieve filter syntax errors, etc., are configurable. As a rule of thumb, error conditions that arise solely in the case of a message addressed to a "local" user have configurable error text, on the presumption  that customized explanations may be useful and are likely to be  comprehensible to someone who corresponds with a "local"  user.

However, error conditions that are more fundamental to the SMTP protocol, that more naturally arise when the MTA is performing a  function of pure SMTP relaying, generally do not have configurable  error text; in such cases where an error response may well be going  back to some remote user who has no connection (not even as a  correspondent) with "local" users, the MTA always emits its  own standard, technically precise, error response.

Keep in mind that all the   error text may potentially be emitted as SMTP  error response text. Thus the values of all these options must conform to the requirements of SMTP error response text. In particular, they are constrained to be in the US-ASCII character set: the MTA will convert any eight bit characters in such option values into the dollar  character,. Also, SMTP responses are limited by the SMTP line length limit (998 characters, not including the final CRLF, and not including the leading numeric error code and extended error code). 

+ Whether the error code used is a temporary 4yz (the default) or a permanent 5yz error code is controlled by the   MTA option.

++ In place of the usual 550 error code, the 530 error code is used when the problem relates to security: as for instance failure to properly authenticate (successfully use SMTP AUTH) when authentication is required.

+++ Errors at MAIL FROM: stage use 450; errors at RCPT TO: stage use 452.

&#x2a; (Added in 8.0.) Whether the error code used is a permanent 5yz (the default) or a temporary 4yz error code is controlled by the   MTA option.

&#x2a;&#x2a; (Added in 8.0) Error regarding null MX for a recipient uses 521 5.1.10; error regarding null MX for a sender uses 550 5.7.26.

Also note that errors authenticating (errors attempting SMTP AUTH use) are a separate category of error type, returning hard-coded error text. (So for instance the  option discussed above is relevant to attempts by the MTA to verify that the user is a currently valid recipient; for instance, that error could be returned as an SMTP rejection of that user&#x27;s address as an envelope recipient address. But an attempt by that same disabled user to submit a message using SMTP AUTH to authenticate would fail authentication and result in a different error, discussed in the table MTA AUTH errors.)   Note that for security reasons, a number of different underlying error conditions cause the same error text to be returned in the SMTP rejection, while more specific details can be provided in the message-id field   of MTA connection transaction logging if the MTA option    is enabled. 

 +Additional detail error text potentially may be suffixed within parentheses for error cases other than a client abort of the AUTH attempt, or successful authentication.

 ++New in 7.3-11.01 version; previously, the   field was the empty string for this success case

See also:
 * Error text and error interpretation MTA options
 * alias_url0 MTA Option
 * viaaliasrequired Option
 * ldap_domain_attr_smarthost MTA Option
 * access_errors MTA Option
 * Access mapping tables
 * ldap_mailhost MTA Option
 * blocklimit Option
 * linelimit Option
 * block_size MTA Option
 * ldap_maximum_message_size MTA Option
 * ldap_blocklimit MTA Option
 * recipientlimit Option
 * FROM_ACCESS mapping table
 * transactionlimit Option
 * ldap_domain_attr_recipientlimit MTA Option
 * ldap_recipientlimit MTA Option
 * ldap_user_status MTA Option
 * ldap_user_mail_status MTA Option
 * ldap_domain_attr_mail_status Option
 * spf_smtp_status_temperror MTA Option
 * spf_smtp_status_permerror MTA Option
 * spf_smtp_status_fail MTA Option
 * spf_smtp_status_softfail MTA Option
 * spf_smtp_status_softfail_all MTA Option
 * spfhelo Option
 * spfmailfrom Option
 * spfrcptto Option
 * log_reason MTA Option
 * returnenvelope Option
 * return_envelope MTA Option
 * MTA options