Save outgoing emails to sentfolder when mailcow is used as a relayhost

I have one server with a website and postfix. I have another server with mailcow dockkerized verision on it. The website uses postfix to connect to my mailcow and sent mails (thus relayhost is my mailcow). The situation: my website needs to show the sent-messages, but it cannot, because the messages sent by postfix are not lcoated int he sentfolder of mailcow . Know what Im saying? Got any idea how to solve this? Maybe some setting in sogo… or something else I missed…