The present invention extends to methods, systems, and computer program products for configuring assurances within distributed messaging systems. A defined set of message log and cursor components are configurably activatable and deactivatable to compose a variety of different capture assurances, transfer assurances, and delivery assurances within a distributed messaging system. A composition of a capture assurance, a transfer assurance, and a delivery assurance can provide an end-to-end assurance for a messaging system. End-to-end assurances can include one of best effort, at-most-once, at-least-once, and exactly once and can include one of: durable or non-durable. Using a defined set of activatable and deactivatable message log and cursor components facilities more efficient transitions between desired assurances. In some embodiments, a composition of a capture assurance, a transfer assurance, and a delivery assurance provides durable exactly-once message delivery.