I've seen some hosts re-try dozens of times every 20 minutes after a 4xx response. That's bad, as it means Google might learn our host to be malicious. smtpproxy should reject repeated delivery attempts by the same host (or host, sender?) within a specific interval.
I've seen some hosts re-try dozens of times every 20 minutes after a 4xx response. That's bad, as it means Google might learn our host to be malicious. smtpproxy should reject repeated delivery attempts by the same host (or host, sender?) within a specific interval.