1. GMail will block your email if you don’t allow one-click unsubscribe. But this is very insecure since anyone can unsubscribe you if you forward your email
Easy Unsubscribe: Implement easy unsubscribe options (One-click Unsubscribe). Gmail users have tools to report spam, unsubscribe from unwanted emails and control their inbox experience. If it is too difficult to unsubscribe from your emails, customers will be more likely to flag your email as spam. Additional links provided in the ‘References’ section at the end of this article.
2. At the same time, Apple’s ITP will start removing all the information from the URL and only leave the domain, if it classifies your site as a “bounce tracker”. This means you won’t even know who to unsubscribe on one click! So all your emails will be blocked.
Gmail does not require one-click unsubscribe, what they actually require is that you include the “List-Unsubscribe” header in bulk emails, with a functioning mailto or http target.
If I forward your newsletter, that’s not a bulk email and it won’t include that header.
This is an important distinction that seems to get glossed over in a lot of the coverage and guides about the recent Gmail and Yahoo changes.
The default forward action in Gmail sends it as content. Forwarding as an attachment is a well-hidden option in the web UI and I just looked in the Gmail mobile app and could not find a way to do it there.
>2. At the same time, Apple’s ITP will start removing all the information from the URL and only leave the domain, if it classifies your site as a “bounce tracker”. This means you won’t even know who to unsubscribe on one click!
Your source doesn't actually say that "ITP will start removing all the information from the URL", only that it will "limit it the same way as third-party cookies" and will be "purging website data in such instances".
Easy Unsubscribe: Implement easy unsubscribe options (One-click Unsubscribe). Gmail users have tools to report spam, unsubscribe from unwanted emails and control their inbox experience. If it is too difficult to unsubscribe from your emails, customers will be more likely to flag your email as spam. Additional links provided in the ‘References’ section at the end of this article.
2. At the same time, Apple’s ITP will start removing all the information from the URL and only leave the domain, if it classifies your site as a “bounce tracker”. This means you won’t even know who to unsubscribe on one click! So all your emails will be blocked.
https://getcake.com/apples-intelligent-tracking-prevention-2...