Most modern devices support "dark mode" for low-light or nighttime environments. This is controlled by individual devices and not by Envoke.
Every app may implement dark mode differently.
Most apps will turn white and close to white backgrounds into black or near-black and font colours will be switched to become light.
Best practices to ensure your emails look good in dark mode:
Use transparent PNGs for logos and icons.
Err on the side of high contrast text colour.
Consider using non-transparent images only if there are critical elements of your message that must show in the defined colours.
Use high contrasts between backgrounds and text to ensure best experience and legibility.
There are custom dark mode CSS solutions that will work in some email clients. Implementation is possible via custom CSS in your email's HTML code. Read more about custom HTML code in email.