> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/unrecognized-internal-address-aad-mismatch.md).

# Unrecognized internal address (AAD mismatch)

### Synopsis

| Field                | Value                                  |
| -------------------- | -------------------------------------- |
| Activation Period    | 14 Days                                |
| Training Period      | 30 Days                                |
| Test Period          | N/A (single event)                     |
| Deduplication Period | 1 Day                                  |
| Required Data        | Microsoft 365 Emails                   |
| Detection Modules    | Email                                  |
| Detector Tags        | Employee Impersonation, Spear Phishing |
| ATT\&CK Tactic       | Initial Access (TA0001)                |
| ATT\&CK Technique    | Phishing (T1566)                       |
| Severity             | Informational                          |

### Description

An email was received from an address using an internal domain, but the sender is not found in Active Directory. This may indicate an impersonation attempt or domain spoofing.

### Attacker's Goals

The attacker aims to impersonate an internal user to gain trust, bypass security controls, and potentially extract sensitive information or distribute malicious content through internal-looking emails.

### Investigative actions

* Verify if the sender address exists in Active Directory.
* Check historical email activity from the spoofed address.
* Review email headers for spoofing indicators (SPF, DKIM, DMARC failures).
* Identify if recipients engaged with the email (clicked links, downloaded attachments).
* Correlate with other alerts involving the same sender or domain.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/unrecognized-internal-address-aad-mismatch.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.