What is Amazon Simple Notification Service $($Amazon SNS$)?$ A cost$-$effective, flexible, and scalable email service that enables developers to send email from within any application A fully managed messaging service for both system$-$to$-$system and application$-$to$-$ person $($A$2$P$)$ communication, which uses publish$/$subscribe patterns A flexible and scalable outbound and inbound marketing communications service that uses email, short message service $($SMS$),$ push, or voice communication channels A serverless event bus that enables easy connection of applications by using data from your own applications, integrated software as a service $($SaaS$)$ applications, and AWS services