Thank you jvstratum.
Well, I finally could make it work, but not really knowing how. I mean this option was already activated. Maybe I wasn't doing things in the right order, I don't know…
I have 3 off topic questions:
When your licence expires, does it mean you won't get any more updates or AcyMaling won't work or send anything at all?
I've noticed when you're reading emails from a dark mode platform (for instance in Gmail, etc.), white sections become black (well, OK, that's the idea of dark mode), red titles become pink, etc. So images with a white background are displayed in some ugly way (ie not melted with the email bg). And the whole thing becomes ugly. Is there a way to get a better result? Like dark mode css or something? The only idea I could get so far has been to use PNG format with transparent bg, which doesn't solve the text color changes.
Oh and one last thing. I noticed there was a possibility to add some custom CSS which is great. But I couldn't make it work. I'm not sure how to use it. Do you have any concrete and simple example of a working content added to this field?
Thank you!