DMZ random disconnects

I had DMZ Enabled on my Network since I need port 25 for my mail server but VM blocks it from being port forwarded, But on my computer this seems to randomly disconnect from Games, Discord. I also tested this on my phone with the issue seeming to be on all devices on the network ( I cannot test the device that the DMZ is on since it is a server ). After disabling it for testing it, My internet seems to be constant and as not cut out once since I have disabled it.

Could I call VM to get them to unblock it? Will they unblock it? Why is it blocked in the first place? ( I looked online and it only said SMB and smth else but not port 25 )