You can find utilities such as the PstViewer Pro (formerly known as EML Viewer Pro) that allows users to export various email messages (.eml, .msg etc) from Outlook or similar programs and save them as images in one of the more common image formats (JPEG, TIFF, PNG etc.).
The very same thing could be probably done with a print screen and pasting the image to a painting program and saving it as images. You would need to manually crop the image and such, but it could work. Another possibility is that you are trying to recover image attachments from old email messages. In this case you have to look for some kind of email recovery utility, not image converter.Open EML file Open JPEG file
A flexible email viewer