All configuration settings should be set before sending the first message.

• Time Configuration
• Transport Configuration -- includes retry delay behavior (RetryDelayBehavior) for mapping exception types to retry delay sequences
• Policies -- Polly-based resilience policies for send operations
• Header Names -- well-known header name constants

Most producer options (delayed processing, message expiration, history tracking) are set at queue creation time via QueueCreationContainer, not on the producer runtime configuration. See your transport's Queue Creation Options page for those settings.