Scott says that when using Office 365 with a mobile device, the images within the letterhead end up as attachments instead of being embedded. Leo says that inline imaging in Office365 is a convenience that Microsoft offers, but it's not a standard, and it ends up as an attachment. He can't control that. There is no fix other than to stop using images in email. The only time that an inline image is displayed is in an email reader that supports it, and he can't control what people use. Email is designed for people to use text and it's just best to stop using corporate logos in emails.