Do you know of any anything more recent on that? It cites the German privacy working group which has no direct influence on the actual laws, and predates GDPR/DSGVO (local German version).
The working group expressed an opinion considering the draft of the GDPR ("In its current prevailing form, we expect email tracking to be categorically prohibited under the GDPR without express user consent.").
I'm not aware of any major change in article 7 since that moment, so I'm fairly confident that opinion is still relevant. If you're asking if it's been tested/challenged in court or in a DP measure, I don't know.
