Why does my signature look wrong in Apple Mail?
This is almost always caused by one of two installation mistakes, both easy to fix.
I copied my signature using Safari, and the layout is off.
Safari can distort signatures when copying — logos and icons may appear oversized and the layout may shift. Copy your signature using Google Chrome or Firefox instead.
My images aren't showing in the Apple Mail signature settings window.
This is normal — it's just how the settings window previews things. Close the settings window and start a new email; your images will load correctly there.
One more thing to check:
Before pasting your signature, uncheck "Always Match My Default Font" in Apple Mail's signature settings. Leaving this checked can also distort your signature's appearance.
For full setup steps, see How do I add an email signature in Apple Mail on macOS?