Kernrechtsfrage
Whether the rent default notice and warning under Art. 257d OR had been effectively served on the tenant.
Extrahierter Entscheid
The notice must actually reach the tenant; mere entry into the tenant's sphere of control is insufficient, and the landlord failed to prove actual receipt.
Extrahierte Begründung
Art. 257d OR requires a receipt-dependent declaration. For an ordinary registered letter, actual receipt by the tenant is decisive. Track & Trace data proves only that a delivery attempt or a delivery occurred, not that the tenant himself received it. The burden of proof lay with the landlord and was not met.