make back-button in mobile interface useful

[derStephan]

RainLoop version, browser, OS:

rainloop v1.12.1
Firefox 62.0.1
Android 7.1

Expected behavior and actual behavior:

Example: I open a mail for reading. When I press normal back button in bottom left corner, firefox leaves the website.

What I expect i: return to message list.

Same applies to all overlays in rainloop like create mail. Whenever I hit back button, the overlay is not closed but the last page in browser history is opened.

This is well acceptable in desktop browsers. In mobile apps however, using the back button is common for "get back to last view". Can you make this common behavior possible for mobile interfaces?