When researching causes of e-mail errors, first read the topic Setting Up for Sending E-Mail and make sure that your system conforms to the recommendations there.
The handling of e-mail outcome codes becomes ever more critical as recipient mail servers devise new methods to combat spam. In particular, the way that CopiaFacts handles multiple MX records can have a significant effect on delivery outcomes.
Often, strategies to improve delivery outcomes can conflict: for example one anti-spam technique involves creating non-functioning or delaying mail servers so that senders who only attempt sending using the first MX record will fail; but against this, attempting to use all MX records when rejected by the first can increase the chances of the sender being blacklisted.
Each MX look-up uses all the available DNS servers shown in the Windows network settings for the network in use by the CopiaFacts node. The configuration command $email_settings specifies the number of retries of MX lookups; but note that if the domain has no A records, the retry of MX look-ups is suppressed. When no MX records have been found, the default is to add the domain name to the list of possible mailservers and attempt an SMTP login to the domain. This action can be suppressed by using an EMAIL_FAIL_NO_MX variable with a non-empty value.
CopiaFacts therefore permits fine control of whether or not you wish to continue attempting transmission to other available mail servers for the target domain after an initial failure. Each single CopiaFacts transmission 'attempt' can include trying to send via all of the mailservers listed in the MX records for the domain. You can specify in the variables MX_CONTINUE and MX_BREAK a blank-separated list of CopiaFacts e-mail outcome codes which will override the default settings for the code and control whether CopiaFacts continues through the list of MX records or breaks out and returns the outcome code.
The default settings are shown in the table below. Actions in bold type cannot be overridden by entering the code in the override variables.
Code |
Default MX Action |
Description |
|---|---|---|
140..145, 153, 156, 158, 166, 167 |
(n/a) |
(e-mail setup errors) |
146 |
Continue |
SMTP send timed out (Socket Error #10060) (see also email option notimeout) |
147 |
Break |
Other SMTP send error |
154 |
Continue |
Remote Host not found (Socket Error #11001 or #10110 or #10102) |
155 |
Continue |
Connection refused (Socket Error #10061) |
157 |
Continue |
No DNS data or no address (Socket Error #11004) |
159 |
Continue |
E-Mail transmission aborted (Socket Error #10053) |
160 |
Break |
TLS connection could not be established |
161 |
Break |
Remote Host unreachable (Socket Error #10064 or #100065) |
162 |
Break |
E-Mail security DLL failed to encrypt/sign this e-mail |
163 |
Continue |
Unexpected disconnect (controlled by email option MX163 in CopiaFacts version 7) |
164 |
Break |
SMTP disconnect signaled before connection |
420 |
Continue |
Resources temporarily unavailable |
421 |
Continue |
Service not available (RFC 2821) |
450 |
Continue |
Requested mail action not taken: mailbox unavailable (RFC 2821) |
451 |
Continue |
Requested action aborted: local error in processing (RFC 2821) |
452 |
Continue |
Requested action not taken: insufficient system storage (RFC 2821) |
500 |
Break |
SMTP command unrecognized (syntax error) (RFC 2821) |
501 |
Break |
SMTP syntax error in command arguments (RFC 2821) |
502 |
Break |
SMTP command not implemented (RFC 2821) |
503 |
Break |
SMTP commands in bad sequence (RFC 2821) |
504 |
Break |
SMTP command parameter not implemented (RFC 2821) |
521 |
Break |
Domain does not accept mail (RFC1846) |
530 |
Break |
Access denied, authentication required (RFC 2554) |
550 |
Break |
Mailbox unavailable (blocked or not found) (RFC 2821) |
551 |
Break |
User not local (try <forward address>) (RFC 2821) |
552 |
Break |
Mailbox has exceeded storage allocation (RFC 2821) |
553 |
Break |
Mailbox name invalid (RFC 2821) |
554 |
Break |
SMTP transaction failed (RFC 2821) |
555 |
Break |
Syntax error |
If you enter a code in both the MX_CONTINUE list and the MX_BREAK list, both entries will be ignored and the default will be used. Any of the codes listed in bold type above will be silently ignored.
Various 5xx error messages can result from a server rejecting a message as an attempt to relay. If you add 'RD' in the value of MX_CONTINUE this will try other MX records when the words 'relay' and 'denied' appear in the error message.
Other References
If you are interested in investigating the causes of specific errors in more detail, see the following links:
