The same newsletter, two builds, shown at phone width. Open this on your own phone for the real test. Toggle our column between the original and the corrected build to see the fix.
What changed in the corrected build (left):
Reliable fonts — dropped the web font phones were stripping; now a clean system stack that renders the same on every device.
Text actually shrinks on phones — mobile sizing now overrides the desktop sizes (it didn't before), so nothing stays oversized or crowds the edge.
Tighter phone margins — more reading width on a narrow screen.