Quote
Sam D.
All others come as "refused"
The returned message should contain a 3-digit return code issued by their mail server. Most commonly, look for either a 4## or 5## code range. The former is a deferred message - I wouldn't worry too much about those, it means the server still has the message in queue but is delayed. The later is some fatal error (mail box full, doesn't exist, incorrect address, etc.). If you see a 5## code, I'd be curious what the number is. Sometimes the reason is spelled out in English "user unknown", "mail box full".