A list of email addresses, domains, or IP addresses that are specifically identified and blocked from receiving emails due to a history of spam complaints, suspicious activity, or violations of email best practices. When an email address or domain is placed on a blocklist, emails sent to or from it may be automatically filtered into spam folders, rejected, or blocked by email service providers and spam filters. For businesses conducting cold email campaigns, adhering to best practices and avoiding placement on blocklists is essential to ensure high email deliverability and maintain a positive sender reputation. Regular monitoring and management of blocklists help improve email outreach effectiveness and compliance with anti-spam regulations.