disabling automatic download of pictures for choosen folders

It is much safer not to have any automatic downloads, and you cannot control it on a per-folder basis. There are a couple of work-arounds. One would be to set junk mail for auto-deletion so you don't have to open individual messages in that folder. I have it auto-delete after a week - this gives me time to look in the folder now and again to rescue anything that shouldn't have gone there. Another would be, before switching to the Junk folder, drag down the separator bar under the message list so that there is no preview window. Now when you select a message Mail won't attempt to open it, so no download happens. Switch back to your inbox (or whatever) and drag it back up again.

AK

Hi JaTo.

It isn’t clear to me what your problem really is. Mail doesn’t download automatically anything when you view a message that has already been marked as junk, regardless of your settings. And if you turn OFF Preferences > Viewing > Display remote images in HTML messages, you won’t have to worry about this problem regardless of whether the message has already been marked as junk or not — as long as you don’t click on any hyperlink or image it may contain, that is...

You may want to read the following article:

How HTML Email Messages Relate to Unsolicited Commercial Email ("spam")