Increase Outreach email body to 800 pixels

For school administrators using GiveCampus Outreach. Controls can differ between the classic email editor and the newer Composer editor.

The classic email editor defaults to a 600-pixel content width; its Style panel exposes padding, colors and borders, not a body-width control. Image width controls do not change that container. Composer uses different controls. Test the delivered layout rather than using a preview width to infer the final email width. Support must identify the editor and verify its available controls before giving an 800-pixel procedure. Do not present an unverified HTML override as a supported setting.