Samsung Galaxy S10 = Email/Gmail

[Android Central Question]

I have Email on pH and also Gmail. I have 2 different email address 1 is for my everyday emails and 2 is where all my folders are kept. When I select All mail (meaning select both boxes) I can only see sub folders for main mail box. I can't select 2 email address subfolders. Can someone please help me. I am on a Galaxy S10 - Sandra