What does “enhanced status code” mean?
Enhanced status codes provide more detailed delivery information than basic SMTP reply codes. While SMTP uses three digit codes (like 250, 450, 550), enhanced status codes add specificity through the RFC 3463 format.
For example, SMTP 550 indicates permanent failure but does not specify why. Enhanced code 5.1.1 means bad destination address. Enhanced code 5.7.1 means policy rejection. This detail enables appropriate bounce handling.
Not all servers provide enhanced status codes, but when available they enable more accurate bounce classification. Systems should parse enhanced codes when present while falling back to basic SMTP code classification when they are not.
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