I expected the messages to be only passed through by my IMAP server from the sending client to the receipient and vice versa.
Messages sent and received are stored in a folder “DeltaChat” on my IMAP server.
There is an archive feature in Delta Chat so I can choose that if I want to keep my messages in a safe place. I have no need for having a copy residing on my server. Besides, most servers only provide limited space for emails. Of course I can automate this process myself by limiting the days to recide in the settings of my server. But not every user has the knowledge to do so or is even aware about that circumstance and they will go off when they find Delta Chat is not able to receive or send any more messages one day.
Maybe I have misunderstood something and this will not be a problem to anyone if he uses his regulary email adress for the use with DeltaChat, but I set up an email account only to use with Delta Chat preserving me from permanently blocking contact attempts from spammers and want to not attend the account on serverside any further.