Terminal event result in focus and desktop switch

My FVWM configuration provides 4x1 desktops. On one desktop I’ve tmux open which sometimes receive events, for example if a new email appear. If that happen FVWM automatically switches to that desktop and provide focus for that terminal / window.

I would like to avoid that, but I couldn’t find any option in my FVWM configuration file how that is possible. Maybe someone have an hint for me?