The outlook window shrinks each time you open it

Under Windows, when you launch software, it is displayed with exactly the same window size. It's been like this forever.
 
In my current and apparently recent version of Outlook, for some time now I have had something completely different: whether I close it completely or just reduce it, the size of the window has decreased significantly the next time I open it. I didn't have this before. I tested by closing and opening several times in a row: the window narrows each time and it ends with a square of 9cm on each side. Depending on the manipulations, the size reduction can be faster but still there.
 
So I have to constantly re-enlarge the window if I want to be able to read my messages or other things. I couldn't find any options in the menus that would fix this and I can't log into my Microsoft account because of the crazy security. In any case, even without a connection in the searches I did which brought me results on the support site yielded nothing.
 
I did a repair on Outlook which didn't solve anything. I'm looking for other avenues.