There are various ways to identify suspicious IP addresses:
1. Email Bounce Rates: High bounce rates can indicate that your email list contains invalid or fake addresses, often associated with suspicious IPs. 2. Spam Complaints: Frequent spam complaints can be a red flag for suspicious activity. 3. Unusual Login Attempts: Multiple failed login attempts from the same IP address can signal suspicious behavior. 4. Geolocation: If you notice logins or activities from regions where you don't usually have subscribers, it might be worth investigating.