The only folder in which remote images should NOT be displayed unless the user clicks on the button is the Spam folder. But that requires SOGo to treat it as a special folder: at the moment, only Inbox, Drafts, Sent and Trash are recognized. That would be useful anyway, since the Spam folder is a standard these days.

I don't agree with you on number 1). Remote images should by default always not be displayed, not only in the spam folder.

Rationale behind this:

• At our University our users can choose, if they want spam emails sorted to a special spam folder or not. So we have users getting spam in the inbox with an added "[SPAM]" in the subject.
• Not all spam is filtered. Not filtered spam has a higher chance of spreading malicious code. So IMHO spam not in the "Spam" folder is more dangerous.

We agree on numbers 2) and 3). This would definitely improve user experience.

Fixed in https://github.com/inverse-inc/sogo/commit/a916ac892703c45fc1c4d720e7baf73c747d45d7

There now is a configurable default in mail preferences where
you can set remote images to display either Never or Always.