Gets the diagnostic code type.
A string value with the diagnostic code type from "Diagnostic-Code" DSN field, or a null reference (Nothing in Visual Basic) if no such field contained in the DSN.
When Action is Failed or Delayed for the given recipient, this field contains the actual diagnostic code type issued by the mail transport.
In this example, DSN field is:
Diagnostic-Code: smtp; Permanent Failure: Other address status
The return value is marked bold.
DsnRecipient Class | MailBee.BounceMail Namespace | DiagnosticCode