Mailbird doesn't yet support DPI/text zooming in Windows, but it will be supported in the near future.
So if you setup Windows to zoom in, you might see parts of emails being cropped.

To fix this, you will have to reduce the Windows DPI zoom level.

1. Open the Windows Control Panel
2. Go to "Display"
3. Click the "Smaller - 100%" option
4. Click "Apply"

Now Windows will ask you to logout, and log back in, and after this, you will be able to view your emails without them being cropped.

Note: We are working on an improvement which will allow you to increase the Windows zoom level.