Open rates were measured (probably) from either track-pixels as well as any normal images hosted by the email provider. When an email is variably considered 'tr

Open rates were measured (probably) from either track-pixels as well as any normal images hosted by the email provider. When an email is variably considered 'trusted'/not-spam by the client, it'll show images. But even if no images are shown, a link clickthrough in the email (to the email host and redirected to source) would then also be added to the open rate.