[Xylakant]

> I fully support legislation that extends the same standard to email

Has already happened. Sending unsolicited marketing via email is illegal in Germany. For some light reading I can recommend this lawyers blog who blogs about his lawsuits against spammers https://www.kanzlei-hoenig.de/search/Spam/

A recent high profile case deciding that even marketing in auto replies constitutes spam was this https://www.dr-bahr.com/news/werbung-in-autoreply-e-mails-is... (with links to high court decisions)

An overview about under which conditions Marketing Mails are legal is here https://www.datenschutzbeauftragter-info.de/fachbeitraege/ne...

You can request that the sender produces a protocol of your opt-in. That’s usually the best route as a layperson since it demonstrates that you know your rights, carries no risk since no accusations are leveled and is a red flag for any lawyers on the other end. I have a link to a good sample text somewhere but can’t find it right now.