I very correctly did that I never uploaded anything to this stock.

that's always been the case - you just have to click to say no

Unfortunately it�s more then saying "no".
They require recaptaning every single photo which hasn�t been sold.

The option is "donate to free section" or "recapture"

where did you see that?  the message we've been discussing is that older unsold images are automatically sent to free section unless you opt out  - 'one click removes them all'

The mail came with a link "to take action" I clicked on and there my unsold images were on display.
I had the option of "donating to free section" or something like "keep online" (don�t remember the exact words).
That was for each picture to be chosen, not once for all, but each picture had it�s own button.

So I chose "keep online" and I got two options: have this picture re-tagged by some professional (I think the price was 6 cent per photo) or tag it myself.

So I chose - tag myself. I didn�t retag it completely just deleted some words and wrote some new tags I hadn�t used before (if they made any sense I did not care).
Then I was able to send the picture back online.

But this means I have to re-tag every unsold single picture on it�s own if I don�t want to donate it.

If I don�t do this it will be automatically moved to the free section.

I�d rather delete my photos before donating them to the free section....

I've been with Dreamtime 5 years and have never received this email and not all my images have sold.