Diagnostic code matching does not seem to be right

[rklec]

Take this diagnostic code in a mail:

Diagnostic-Code: smtp; 550 5.1.1 <[email protected]> User doesn't
    exist: [email protected] 

As per it's RegEx defined in the source.

MailBounceDetector/MailBounceDetector/BounceDetectResult.cs

Line 22 in 413ea4b

["Diagnostic-Code"] = R(@"(.+);\s*([0-9\-\.]+)?\s*(.*)"),

https://regex101.com/r/pKmRdj/1

This results in two groups being matched and then also listed:

• 550
• 5.1.1 <[email protected]> User doesn't

Here the relevant sepc part: https://www.rfc-editor.org/rfc/rfc3464#section-2.3.6

The diagnostic-type is `smtp´ in this case, but could be something different - it is just skipped for some reason? (Note I also don't get what valöues it should contain it talks about some IANA specification in https://www.rfc-editor.org/rfc/rfc3464#page-32 and https://www.rfc-editor.org/rfc/rfc3464#section-2.1.2, but well maybe it also doe snot matter.)

As per spec, then a semicolon follows and some arbitrary text:

diagnostic-code-field = "Diagnostic-Code" ":" diagnostic-type ";" *text

So I don't quite see the sense, why the regex splits it up again?
In my case, the status is again reported and I am not sure what 550 is supposed to mean. In any case, it's no new type?

So maybe just output the whole thing as a string instead? The parsing seems to make no sense?
Or do I miss some spec here that clearly defines that there are numbers in there?

[rklec]

Okay the -typethings are usual stuff in the spec, maybe it is not wrong. But is the value dns. Apparently it is always dns: https://www.rfc-editor.org/rfc/rfc3461#section-9.3 Likewise the smtp for Diagnostic code: https://www.rfc-editor.org/rfc/rfc3461#section-9.2

So maybe splitting that away is okay, but anyway the part afterwards is strange to me...