# Transactions and delivery guarantees

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The RabbitMQ transport supports the following [transport transaction modes](/transports/transactions.md):

 * Transport transaction - receive only
 * Unreliable (transactions disabled)


## Transport transaction - receive only

In `ReceiveOnly` mode, messages are consumed in manual acknowledgment mode. Successfully processed messages are acknowledged via the AMQP [basic.ack](https://github.com/rabbitmq/amqp-0.9.1-spec/blob/b8e975a762b8677263ebbbba1e70654b5263af81/xml/amqp0-9-1.xml#L2565-L2594) method, at which point the broker will remove them from the queue. Failed messages that need to be retried are re-queued via the AMQP [basic.reject](https://github.com/rabbitmq/amqp-0.9.1-spec/blob/b8e975a762b8677263ebbbba1e70654b5263af81/xml/amqp0-9-1.xml#L2598-L2658) method.

> [!WARNING]
> If the connection to the broker is lost before a message can be acknowledged, even if the message was successfully processed, the broker will automatically re-queue the message. This will result in the endpoint processing the same message multiple times.

## Unreliable (transactions disabled)

Like in `ReceiveOnly` mode, messages are consumed in manual acknowledgment mode. Regardless of whether a message is successfully processed, it is acknowledged via the AMQP [basic.ack](https://www.rabbitmq.com/amqp-0-9-1-quickref.html#basic.ack) method after the processing attempt. This means a message will be attempted once and moved to the error queue if it fails.

> [!WARNING]
> Since manual acknowledgment mode is being used, if the connection to the broker is lost for any reason before a message can be acknowledged, the broker will automatically re-queue the message. If this occurs, the endpoint will retry the message despite the transaction mode setting.