Thank you for your help, Alo!
Tracking pixel is added all right, Spamassassin treats it like a normal image.
Unfortunately, it doesn’t track.
I copied tr.php to website root folder, changed “no” to “yes” in the line below,
if ( get_option(‘alo_em_use_tracking_pixel’) == ‘yes’ ) exit;
but it doesn’t track.
I’ll have to check something else…
Thanks.
Marco.