How should I handle soft bounces?
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A soft bounce is a temporary delivery failure. The receiving server accepted your connection but couldn't deliver the message at that moment, and it expects you to try again. The causes are usually temporary: the mailbox was full, the server was briefly down, or a rate limit triggered for your sending IP.
Unlike hard bounces, soft bounces don't require immediate removal. But they do require watching.
How your ESP handles them by default. Most ESPs retry soft bounces automatically over a window of 24-72 hours. If delivery succeeds on a retry, the bounce is resolved and you don't need to do anything. If the message expires without delivery, the ESP typically logs it as a failed soft bounce. Check your platform's documentation to understand exactly when and how it retries, because this varies significantly between providers.
When soft bounces become a concern. One soft bounce from an address is nothing to worry about. But if the same address soft bounces repeatedly across multiple campaigns, that pattern suggests a more persistent problem. The mailbox might be abandoned but not yet recycled, or the domain might be experiencing longer-term issues. A common threshold: if an address soft bounces on three or more consecutive sends, treat it like a hard bounce and remove it. Some ESPs apply this automatically.
Soft bounces that are actually soft hard bounces. Some providers return 4xx codes (technically a soft bounce) for what is effectively a permanent rejection. Policy blocks and blocklist rejections sometimes come back as 4xx responses depending on how the receiving server is configured. If you see the same policy-related soft bounce message repeatedly, investigate the underlying cause rather than just retrying.
If you're seeing a sudden spike in soft bounces across your list, it's often a sender reputation issue or a rate-limiting response from a specific mailbox provider. That's worth investigating before the next send rather than waiting for retries to sort it out.
Not sure what your bounce types mean or how to read them in your ESP? Reach out and we'll help you decode them.
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