A friend sent me an email with a JPEG photo in the middle of the text. The picture is so big, most of it is outside the screen and I want to view it with an outside image viewer and not in Gnus. How do I save an image that is included in the email in Gnus, if it's not just an ordinary attachment?
The command you need is
gnus-summary-save-parts. You have an inline image, which implies that you received an HTML mail. An inline image is an instance of a so-called MIME part, where MIME is an Internet standard governing email-related things such as non-text attachments.