Managing multiple client accounts efficiently requires email marketing software with robust multi-client management features. Look for platforms that provide agency-specific tools, such as sub-accounts, user permissions, and white-labeling options. Utilize project management features to keep track of different campaigns and client requirements. Automate repetitive tasks and set up standardized templates to save time. Regularly communicate with your clients to understand their needs and provide them with detailed reports on campaign performance. Data security and compliance with regulations like GDPR are also critical when handling multiple client accounts.