# Until Successful, reconnection and redelivery policies

*MuleSoft Platform Integration Architect Study Guide · Designing integration solutions to meet reliability requirements · Last updated November 13, 2026 · https://www.certifyforce.com/study-guide/mulesoft-platform-integration-architect/designing-integration-solutions-to-meet-reliability-requirements/until-successful-reconnection-and-redelivery-policies*

Tell Mule's three retry mechanisms apart by the failure each one handles: reconnection strategies for connections that cannot be established, Until Successful for processors that fail inside one event, and redelivery policies (or an Anypoint MQ dead-letter queue) for messages that keep failing, including how each behaves inside a transaction.

- Certification: Salesforce MuleSoft Platform Integration Architect
- Exam section: Designing integration solutions to meet reliability requirements
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-platform-integration-architect

**Official exam objective:**

> Recognize the purpose and characteristics of Until Successful scope, reconnection strategies, and redelivery policies.

## What the exam expects

- Match a failure to its mechanism: a connection that cannot be established, a processor that fails inside an event, or a message that fails on every delivery.
- Predict reconnection behavior from the configured strategy and its defaults, including what happens at deployment.
- Recognize how Until Successful retries, how long it waits, what it raises, and what it does to threads inside a transaction.
- Configure a redelivery policy and handle `MULE:REDELIVERY_EXHAUSTED` so a poison message leaves the source, and recognize the Anypoint MQ queue-level alternative.

**Reconnection strategy**: how an operation or source re-establishes a connection after failing to connect. **Until Successful**: a scope that retries the processors inside it until they all succeed or retries run out. **Redelivery policy**: a filter on a flow's source that limits how many times Mule processes a message that keeps raising errors. **Poison message**: a message that fails on every attempt. **Dead-letter queue (DLQ)**: a queue that receives messages that could not be delivered ([Reconnection Strategies](https://docs.mulesoft.com/mule-runtime/latest/reconnection-strategy-about), [Until Successful Scope](https://docs.mulesoft.com/mule-runtime/latest/until-successful-scope), [Configure a Redelivery Policy](https://docs.mulesoft.com/mule-runtime/latest/redelivery-policy), [Configuring and Using Queues](https://docs.mulesoft.com/mq/mq-queues)).

## Key facts

| Fact | Detail | Source |
|---|---|---|
| No reconnection strategy | Default None: immediate connectivity error. | [Reconnection Strategies](https://docs.mulesoft.com/mule-runtime/latest/reconnection-strategy-about) |
| `reconnect` defaults | `count` 2, `frequency` 2000 ms. | [Reconnection Strategies](https://docs.mulesoft.com/mule-runtime/latest/reconnection-strategy-about) |
| `reconnect-forever` | Retries at `frequency` (default 2000 ms) while the app runs. | [Reconnection Strategies](https://docs.mulesoft.com/mule-runtime/latest/reconnection-strategy-about) |
| `failsDeployment` | Default `false`; `true` fails deployment when the test connection fails. | [Reconnection Strategies](https://docs.mulesoft.com/mule-runtime/latest/reconnection-strategy-about) |
| Until Successful retries | All processors in the scope, synchronously. | [Until Successful Scope](https://docs.mulesoft.com/mule-runtime/latest/until-successful-scope) |
| `millisBetweenRetries` | Minimum gap, default 60000 ms, at most about twice the value. | [Until Successful Scope](https://docs.mulesoft.com/mule-runtime/latest/until-successful-scope) |
| Until Successful in a transaction | Blocks the thread between retries. | [Transaction Management](https://docs.mulesoft.com/mule-runtime/latest/transaction-management) |
| Max Redelivery Count | Default 5; error when failures exceed it. | [Configure a Redelivery Policy](https://docs.mulesoft.com/mule-runtime/latest/redelivery-policy) |
| Redelivery counter store | Nonpersistent default, `entryTtl` 300 s. | [Configure a Redelivery Policy](https://docs.mulesoft.com/mule-runtime/latest/redelivery-policy) |
| On Error Continue in a transaction | Transaction stays active and can commit. | [Transaction Management](https://docs.mulesoft.com/mule-runtime/latest/transaction-management) |
| MQ DLQ delivery attempts | Default 10, range 1-1000. | [Configuring and Using Queues](https://docs.mulesoft.com/mq/mq-queues) |
| MQ acknowledgement timeout | Two minutes when not set. | [Anypoint MQ ACK and NACK Operations](https://docs.mulesoft.com/anypoint-mq-connector/latest/anypoint-mq-ack) |

## Check yourself

- Why can the real gap between Until Successful attempts be longer than `millisBetweenRetries`?
- When would you set `blocking="false"` on a reconnection strategy?
- What error does a Database Connector operation raise when it cannot connect and no strategy is configured?
- When does Mule evaluate a source's redelivery policy relative to the rest of the flow?

## Sources

- [Reconnection Strategies](https://docs.mulesoft.com/mule-runtime/latest/reconnection-strategy-about)
- [Until Successful Scope](https://docs.mulesoft.com/mule-runtime/latest/until-successful-scope)
- [Configure a Redelivery Policy](https://docs.mulesoft.com/mule-runtime/latest/redelivery-policy)
- [Transaction Management](https://docs.mulesoft.com/mule-runtime/latest/transaction-management)
- [Configuring and Using Queues](https://docs.mulesoft.com/mq/mq-queues)
- [Anypoint MQ ACK and NACK Operations](https://docs.mulesoft.com/anypoint-mq-connector/latest/anypoint-mq-ack)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 7 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Platform Integration Architect pack (USD $19): https://www.certifyforce.com/practice-exams