Content of folder "Contact replies" not stored when settings are saved

My software
My Mautic version is: 4.2.2
My PHP version is: ???
My Database type and version is: ???

My problem
My problem is:

Dear forum,

I am using “Mautic Cloud Hosting” from hartmut.io, that means they are providing the server architecture and installation for me. During setup of Mautic I used a particular E-Mail address within my domain, fetched the E-Mail folders for the monitored inbox and selected “Inbox” as the folder to check for contact replies.

Now since my setup was working I wanted to change the E-Mais address to a different one within the same domain (technically it should be the same), but for some reason, Mautic is not able to remember the fetched folders from this E-Mail address. Mautic is able however, to fetch them and lets me choose one to monitor for contact replies. But as soon as I hit the save button, those fetched folders disappear and a default “INBOX” folder appears as the selection. The way it is set up now, Mautic does not detect whether a contact replies.

Steps I have tried to fix the problem: Following the suggestion of the support of my hosting service, I cleared the cache and tried again to save the folders, but nothing changed.

Does anyone have an idea, what else I could check or do to fix this?

Your help is much appreciated!
Stefan