Dark mode email
How an email looks when the reader’s client inverts or recolours it.
Mail clients handle dark mode differently. Some leave the email alone, some swap the background, and some rewrite colours throughout — including inside images and text you set explicitly.
The usual casualties are logos saved as black artwork on a transparent background, which vanish, and text whose colour was left to the default and gets inverted into something unreadable.
The reliable defences are dull ones: set both text and background colours explicitly, avoid pure black and pure white, and give logos a version that survives on a dark ground.