Network Prevent for Email originated responses and codes

Network Prevent for Email
Originated Responses and Codes

Network Prevent for Email
originates the following responses. Other protocol responses are expected as
Network Prevent for Email
relays command stream responses from the forwarding MTA to the sending MTA.
Network Prevent for Email
originated responses
shows the responses that occur in situations where
Network Prevent
must override the receiving MTA. It also shows the situations where
Network Prevent
generates a specific response to an event that is not relayed from downstream.
“Enhanced Status” is the RFC1893 Enhanced Status Code associated with the response.
Network Prevent for Email
originated responses
Code
Enhanced Status
Text
Description
250
2.0.0
Ok: Carry on.
Success code that
Network Prevent for Email
uses.
221
2.0.0
Service closing.
The normal connection termination code that
Network Prevent for Email
generates if a QUIT request is received when no forward MTA connection is active.
451
4.3.0
Error: Processing error.
This “general, transient” error response is issued when a (potentially) recoverable error condition arises. This error response is issued when a more specific error response is not available. Forward connections are sometimes closed, and their unexpected termination is occasionally a cause of a code 451, status 4.3.0. However sending connections should remain open when such a condition arises unless the sending MTA chooses to terminate.
421
4.3.0
Fatal: Processing error. Closing connection.
This “general, terminal” error response is issued when a fatal, unrecoverable error condition arises. This error results in the immediate termination of any sender or receiver connections.
421
4.4.1
Fatal: Forwarding agent unavailable.
That an attempt to connect the forward MTA was refused or otherwise failed to establish properly.
421
4.4.2
Fatal: Connection lost to forwarding agent.
Closing connection. The forwarded MTA connection is lost in a state where further conversation with the sending MTA is not possible. The loss usually occurs in the middle of message header or body buffering. The connection is terminated immediately.
451
4.4.2
Error: Connection lost to forwarding agent.
The forward MTA connection was lost in a state that may be recoverable if the connection can be re-established. The sending MTA connection is maintained unless it chooses to terminate.
421
4.4.7
Error: Request timeout exceeded.
The last command issued did not receive a response within the time window that is defined in the RequestProcessor.DefaultCommandTimeout. (The time window may be from RequestProcessor.DotCommandTimeout if the command issued was the “.”). The connection is closed immediately.
421
4.4.7
Error: Connection timeout exceeded.
The connection was idle (no commands actively awaiting response) in excess of the time window that is defined in RequestProcessor.DefaultCommandTimeout.
501
5.5.2
Fatal: Invalid transmission request.
A fatal violation of the SMTP protocol (or the constraints that are placed on it) occurred. The violation is not expected to change on a resubmitted message attempt. This message is only issued in response to a single command or data line that exceeds the boundaries that are defined in RequestProcess.MaxLineSize.
502
5.5.1
Error: Unrecognized command.
Defined but not currently used.
550
5.7.1
User Supplied.
This combination of code and status indicates that a Blocking response rule has been engaged. The text that is returned is supplied as part of the response rule definition.
Note that a 4xx code and a 4.x.x enhanced status indicate a temporary error. In such cases the MTA can resubmit the message to the
Network Prevent for Email
Server. A 5xx code and a 5.x.x enhanced status indicate a permanent error. In such cases the MTA should treat the message as undeliverable.