Email Security: How to troubleshoot NDR's.

10/29/2024 1,036 People found this article helpful 486,160 Views

Description

I do not receive NDR's, How can I see what message was rejected?

Resolution

In Email Security go to the Manage | Server | Advanced | Download System/Log Files | pmta:mta-log and download the MTA hourly log for the time the original message was sent.

Keep in mind that these are logged in GMT so you will need to add hours according to the time zone you are in.

Listed below is the general ESMTP response codes you may see listed in an SMTP conversation.

ESMTP STATUS CODE	DESCRIPTION
211	System status, or system help reply
214	Help message (Information on how to use the receiver or the meaning of a particular non-standard command; this reply is useful only to the human user)
220	Service ready
221	Service closing transmission channel
250	Requested mail action okay, completed
251	User not local; will forward to
354	Start mail input; end with "."
421	Service not available, closing transmission channel (This may be a reply to any command if the service knows it must shut down)
450	Requested mail action not taken: mailbox unavailable (E.g., mailbox busy)
451	Requested action aborted: local error in processing
452	Requested action not taken: insufficient system storage
500	Syntax error, command unrecognized (This may include errors such as command line too long)
501	Syntax error in parameters or arguments
502	Command not implemented
503	Bad sequence of commands
504	Command parameter not implemented
550	Requested action not taken: mailbox unavailable (E.g., mailbox not found, no access)
551	User not local; please try <....>
552	Requested mail action aborted: exceeded storage allocation
553	Requested action not taken: mailbox name not allowed (E.g., mailbox syntax incorrect)
554	Transaction failed

For specific codes for Microsoft Exchange please see their KB: http://support.microsoft.com/kb/284204

There are also many other documents in the Microsoft KB depending on the NDR you are seeing.

Depending on the type of Email Server you use and the type of server your sending to , you may see different messages.
However the numbered code will always be the same on an NDR.
BATV (Bounce Address Tag Validation) can also cause issue with not recieving an NDR and Out of Office replies
BATV will drop an NDR or Out of Office reply if the mail from address is a NULL value.
NOTE: Exchange settings prevent an NDR or a Out of Office reply from using the original recipients email address in the mail from field and will alter to a NULL value if it is destined for outside of the local network.
The only fix for this and to be able to get NDR's or Out of Office replies would be to either alter the default behavior of the Email Server or to turn off BATV.
If BATV is turned off and you still do not get any NDR's or Out of office replies then it may be possible that an internal MX and A record does not exist on your internal DNS server for your own domain.
The MTA does MX record routing, so when an NDR is generated by the local outbound MTA to the original sender the MX lookup returns the public IP address to route to.
Depending on firewall settings these will not be returned to the internal email server unless a local record exists to point to the internal email server or a look back policy is set in the firewall to direct the SMTP traffic destined for the public IP of the MX record back to the internal mail server private IP address.

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Email Security: How to troubleshoot NDR's.

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