The basic reliability mechanisms in JMS that ensure message delivery are:

1. Message Acknowledgement – Various levels of acknowledgement can be specified for a message.
2. Message Persistence – Messages should be specified as PERSISTENT, meaning they must not be lost in the event of a provider failure.
3. Message Priority –  Priority levels for messages can be set, which can affect the order in which the messages are delivered.
4. Message Expiration Time – An expiration time for messages can be set, so they will not be delivered if they are obsolete.
5. Temporary Destination – Temporary destinations can be created that last only for the duration of the connection in which they are created.