Bounce messages and codes are simply reported to the software and not generated by it.  Most internet and email service providers will customize their outgoing bounce messages to conform to their network's terms of service, but there is a standard set of codes in use across the entire internet globally. For the latest and most accurate information, please visit our email resource center:

https://bb-email-services.docs.blackbaud.com/faqs/processing/#ProcessingBounce