Google has announced new measures to combat spam targeting Gmail users. These changes aim to enhance the security and reliability of email communication.

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 Will Ask Users to Verify Suspicious Actions on Gmail
If the system detects potentially suspicious activity, it will require additional identity verification, such as entering a code from an SMS or secondary email. If verification fails, a notification requesting confirmation will be sent to trusted devices.
Recorded News — Tech NewsBradley Rhodes

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.