Bulk senders who send over 5,000 emails to Gmail addresses daily will now be required to include an easy unsubscribe button in their messages. Additionally, they must verify their email addresses, confirming they are the legitimate owners of their domain names.
Google has also cautioned that it will cease delivering emails from senders frequently reported as spam. According to Google's Postmaster tools, the threshold for this is 0.3% of sent messages.
These steps underscore Google's ongoing battle against spammers. Despite using machine learning techniques to combat spam, spammers continually find new ways to bypass filters.