SYMPTOM:
Documents received through Gmail don't have the right formatting. Images are missing, any formatting to text and grids is lost, as well as any thresholds.
CAUSE:
Wrong settings.
ACTION:
In developer, go to Administration > Delivery managers > Devices, double click the device being used for Gmail, e.g. General Email shown below. Click Options to open MIME setting.

Check all of those settings, especially “Use only tables to position elements in HTML” and “Use inline style CSS”.

Article Reference Number: KB441420