---
title: "SMIME Assertion"
description: "Configure the JMeter SMIME Assertion assertions: properties, defaults, and practical usage notes for building reliable load tests."
url: https://docs.jmeter.ai/components/smime-assertion/
lastUpdated: 2026-10-01
source: docs.jmeter.ai
---

# SMIME Assertion

*Part of the **Assertions** category. Also documented in context in the [full Component Reference](/user-manual/component-reference/#smime-assertion).*

![SMIME Assertion](/images/screenshots/assertion/smime.png)

The SMIME Assertion can be used to evaluate the sample results from the Mail Reader Sampler.
This assertion verifies if the body of a mime message is signed or not. The signature can also be verified against a specific signer certificate.
As this is a functionality that is not necessarily needed by most users, additional jars need to be downloaded and added to `JMETER_HOME/lib`:

- `bcmail-xxx.jar` (BouncyCastle SMIME/CMS)
- `bcprov-xxx.jar` (BouncyCastle Provider)

These need to be [downloaded from BouncyCastle.](http://www.bouncycastle.org/latest_releases.html)

If using the [Mail Reader Sampler](/components/mail-reader-sampler/),
please ensure that you select “`Store the message using MIME (raw)`” otherwise the Assertion won’t be able to process the message correctly.

| Name | Required | Description |
| --- | --- | --- |
| Name | No | Descriptive name for this element that is shown in the tree. |
| Verify Signature | Yes | If selected, the assertion will verify if it is a valid signature according to the parameters defined in the `Signer Certificate` box. |
| Message not signed | Yes | Whether or not to expect a signature in the message |
| Signer Certificate | Yes | ”`No Check`” means that it will not perform signature verification. “`Check values`” is used to verify the signature against the inputs provided. And “`Certificate file`” will perform the verification against a specific certificate file. |
| Message Position | Yes | The Mail sampler can retrieve multiple messages in a single sample.     Use this field to specify which message will be checked.     Messages are numbered from `0`, so `0` means the first message.     Negative numbers count from the LAST message; `-1` means LAST, `-2` means penultimate etc. |

## Related

- [Assertions & SLA Validation](/topics/jmeter-assertions-guide/)
- [Full Component Reference](/user-manual/component-reference/)
- [Functions and Variables](/user-manual/functions/)