How to Read Shared Mailbox Emails Programmatically Using Graph API Without Outlook

Question

Hello,

A need has arisen to read Shared Mailbox emails programmatically without requiring the Outlook application to be active at all times, using the Graph API.

The Shared Mailbox is set to allow specific users access to read emails, and the mailbox is granted to those users.

Access to the Shared Mailbox emails is available through both app-based and web-based Outlook.

For authentication, Truu is used, which is similar to Okta.

An app has been registered with Mail.Read, Mail.Read.Shared, User.Read permissions under Delegated permissions.

Below is the Python code used to obtain an access token:

AUTHORITY = f"https://login.microsoftonline.com/{TENANT_ID}"
SCOPE = ["https://graph.microsoft.com/Mail.Read.Shared"]
def get_token():
# Initialize the client app for user-based authentication
app = msal.PublicClientApplication(
CLIENT_ID,
authority=AUTHORITY
)
result = app.acquire_token_by_username_password(
USER_ACCOUNT,
USER_PASSWORD,
scopes=SCOPE
)
if "access_token" in result:
return result["access_token"]
else:
raise Exception("Could not acquire token:", result.get("error"), result.get("error_description"))

Currently, an error is encountered: "An error occurred: WSTrust server returned error in RSTR: {'reason': 'Authentication failed', 'code': 'wst:FailedAuthentication'}"

Assistance in troubleshooting this issue would be greatly appreciated.

Answer 1

Hello Matthew Marron,

Thank you for reaching out to Microsoft Support!

Outlook applications do not need to be active when you need to programmatically read emails from shared mailboxes using the Graph API, and application registered in Azure AD need to grant delegated permissions that you have already granted. However, it is important to note that Mail.Read.Shared permissions are only valid for work or school accounts.

Then you get Authentication failed when you get the token with the username and password, it is recommended that you use the SDK to get the access token, see the documentation for details and also provide code examples.

Get the Graph API endpoint for shared mailbox messages:

https://learn.microsoft.com/en-us/graph/outlook-share-messages-folders

Hope this helps.

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