Postmark is a transactional email service for SaaS products, e-commerce companies, and software teams that need reliable delivery for receipts, notifications, password resets, and product messages. Its referral partner program is relevant for developers, agencies, email consultants, and infrastructure publishers whose audiences need dependable email sending. It provides a referral partner program and tracks the program through Rewardful. It is relevant because transactional email buyers often evaluate deliverability, uptime, support quality, and API fit before choosing a provider.