What is a soft bounce?
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A soft bounce is a temporary delivery failure. The receiving server answers with an SMTP 4xx code. Something got in the way for now, and the address might accept your email later. The mailbox is full, the server is down for maintenance or overloaded, or it is rate-limiting you for the moment.
Most ESPs retry soft bounces automatically over the next 24 to 72 hours. If they keep failing, some ESPs convert the address to a hard bounce after a set number of failures in a row, so check your platform's settings to see where that line sits. And watch for addresses that soft bounce again and again over weeks. That pattern often means the mailbox is abandoned, and those addresses belong on your suppression list too.
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