Greylisting, Tarpitting, and Other Receiver Defenses Senders Should Understand
Receiving servers defend themselves with deliberate delays, temporary rejections, and traps for impatient senders. How each defense works and how a good MTA passes them.
2 articles with this tag
Receiving servers defend themselves with deliberate delays, temporary rejections, and traps for impatient senders. How each defense works and how a good MTA passes them.
Hard versus soft is not enough. How SMTP codes, enhanced status codes, and provider quirks should drive your retry, suppression, and reputation logic.