Subscriptions
Dunning
Dunning is the automated process a subscription business runs after a payment fails: retrying the charge, notifying the customer, and requesting an updated payment method.
Effective dunning branches on the issuer decline code rather than applying one schedule to every failure. A hard decline such as a closed account will never succeed on retry, and attempting it anyway accumulates declines against your merchant profile for no possible gain.
The emails are the visible part and the smallest part. Most recoverable failures resolve without contacting anyone — the card was fine and the account was briefly short, or the credential was reissued and an updater service refreshed it. Email matters for the residual where the credential is genuinely dead, and there the deciding factor is whether the update link works without a login.
In depth: What is dunning?