Hi Tristan, Hope you are doing well. We need to understand one concept that the bounce is not generated by the adobe campaign but it depends on the response coming from that domain, as you said it doesn’t happen usually it could be possible the domain is sending the bounce some time, it usually happens with private domains. You could get more details by checking the MTA and MTA CHILD logs on your system, Home > Monitoring > Process List > Open Log. Secondly: you could also ask the adobe support ...