Notes:
The email doesn't actually use the stylesheet being fetched, it's purely for tracking.
The rule I use won't be good as all the links in the email point to that domain.
Possible rules:
g2a-com.newsletter.com.pl/so.php$third-party
g2a-com.newsletter.com.pl/*.gif$third-party
Not going to touch the part that I was the one who somehow did the "ignoring" here. Anyway...
The rule you added is flawed. The URL is .com.pl but the rule you added is .com (see original post).
See your PMs for a link with the full unmasked link to the stylesheet for proof that it's blank. Again the reason I state it's for tracking is due to the unique hash being used in the URL.