When an email sender finds their emails blocked by Gmail globally, it is usually due to violating Google's Bulk Sender Guidelines.
Google maintains a "blocked list" logic based on reputation signals: gmail blocked email list
The blocking mechanism is a critical layer of cybersecurity. When an email sender finds their emails blocked
Under "Contacts," tap to see accounts blocked across all Google services (including Gmail). Pro Tip: Check Your Spam Folder gmail blocked email list