Bounce Handling & Definitions

The "best practice" rules for returned mail. This section defines the industry standards: 1 Hard Bounce = Suppress Immediately. 3-5 Soft Bounces in a row = Treat as Hard. A good sender knows when to stop trying to deliver to a closed port.

19 questions in this topic

How should I handle hard bounces? How should I handle soft bounces? What are common hard bounce reasons? What are common soft bounce reasons? How many soft bounces before suppressing an address? Does my ESP handle bounce processing automatically? What’s the difference between hard, soft, and transient bounces? What does “user unknown” mean? What is “mailbox full”? What are “policy” or “spam-related” bounces? What is “relay denied”? What is “message too large”? What are graylist-related deferrals? How do spam-block errors appear in bounce logs? How to normalize bounce codes across providers? What is “too many connections” or “rate limit” bounce? What’s the difference between temporary and persistent deferrals? How to identify false bounces from filters or blocklists? What’s the lifespan of a bounce event for hygiene rules?

Questions about Bounce Handling & Definitions