NDR Codes

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With the release of version 3.8.11.12, Alligate will now return NDR codes when a message or command is refused.

 

For standard refusals Alligate uses standard Microsoft Exchange NDR codes. Because the range of standard codes does not accommodate the various methods Alligate uses to refuse messages, it was necessary to "invent" codes of our own. Non standard codes are indicated below in blue. These codes will help our users better track issued where a message may have been refused erroneously.

 

Please note: These codes apply only to Alligate generated responses. Responses that are relayed from the mail server to the remote server will remain unchanged.

 

 

CODE

MEANING

4.8.1

Greylist "Try Again Later" refusal

5.2.1

Message size too large

5.4.8

Possible loop condition

5.5.1

Invalid recipient

5.5.2

Command out of sequence

5.5.3

Too many invalid recipients or failed Greylist failures in a single connection.

5.5.6

Excessive backscatter coming into a particular address

5.7.1

General refusal based on user defined rejection rules

5.7.2

Country not allowed

5.8.1

Sender is on temporary blacklist

5.8.2

Sender is on temporary blacklist for disconnecting during tarpitting

5.8.3

Sender is on temporary blacklist for excessive invalid recipients or excessive Greylist failures

 

4.x.x codes are returned with 4xx responses. 5.x.x codes are returned with 5xx responses.