When active customer emails are suppressed in transactional email tools like SES, a multi-faceted approach is crucial. First, investigate the cause of suppression (bounces, complaints, etc.) and handle each appropriately. Automated systems should remove suppressed addresses to protect sender reputation, with continuous monitoring of bounce and complaint rates using tools like Amazon CloudWatch. Prioritize email list hygiene through segmentation, removal of inactive subscribers, and avoiding purchased lists. Ensure emails are truly transactional, providing value and relevance. Implement double opt-in, warm up IPs, and authenticate the domain using SPF, DKIM, and DMARC. Communicate with affected users and provide options for them to manage their subscriptions.