What DENIC is, and why .de behaves differently
DENIC eG is a registered cooperative in Frankfurt am Main whose members are the providers that sell .de names, and it runs the registry without the intention of making a profit rather than under an ICANN registry agreement. The consequence for a buyer is that the habits carried over from .com do not transfer. There is no auto-renew grace period, no 60-day transfer lock, and the contract that actually governs the name is between you and DENIC directly, not between DENIC and your provider.
That direct contract is the detail worth understanding, because it is what makes .de unusually hard to lose by accident and unusually confusing when something goes wrong. Cancelling the service agreement with a hosting company does not cancel the domain contract with DENIC. The provider simply stops administering the name, DENIC picks it up, and the holder starts receiving letters from Frankfurt about a domain they thought they had given up. Nothing is broken when that happens; it is the system working as designed, and the fix is either a provider transfer to us or a deletion request.
Three states people confuse, and how we handle each
A .de that stops working is in one of three quite different states. If it was deleted, it is in the Redemption Grace Period and can be taken back until the 31st day, which is the closest thing .de has to a gTLD redemption. If your provider walked away, it is in TRANSIT, still resolving, waiting for you to answer a letter. If DENIC could not verify the holder data, it has been taken out of the zone under the BSI Act obligations and you have 83 days to complete verification through your provider before the contract ends. That last case is the one with no safety net: the Domain Guidelines specifically exclude a termination for unverifiable holder data from the Redemption Grace Period, so there is nothing to restore afterwards.
As a reseller our job is to keep you out of the third case and to act quickly in the first two. That means submitting a holder record DENIC can verify at the outset rather than a placeholder, keeping the postal address current because TRANSIT letters go by post, and passing on verification requests the day they arrive rather than at the end of the month. We cannot verify anything on DENIC's behalf and we cannot extend a DENIC deadline, but almost every .de lost in practice is lost to an unopened letter rather than to a policy.