email tracking, is it possible in fedora mail clients?

[stan]

Hi,
I just saw this article via Pocket in firefox,
https://www.vox.com/recode/23332959/email-tracking-privacy
and I wondered if that is an issue in fedora.  It seems that in order
for such tracking to work, it has to have the cooperation of the
operating system, or at least the mail client.  And, I would think that
open source mail clients don't allow that.  Am I right?