Investigate environmental factors

Oct 13, 2025 by wbrum.org 82 views

Outlook on Mac: messageParent Fails on Some Machines, Potentially Linked to &action=displayDialog vs. _host_Info

Microsoft Outlook is a widely used email client that provides a range of features and integrations to enhance user experience. However, some users have reported issues with the messageParent function in Outlook on Mac, which fails to send messages from the child dialog to the parent task pane on some machines. This issue is potentially linked to the use of &action=displayDialog instead of the expected _host_Info in the dialog URL. In this article, we will delve into the details of this issue, explore possible causes, and discuss potential solutions.

To better understand the issue, it's essential to provide information about your environment. Here are the details:

Platform: Mac
Host: Outlook
Office version number: 16.94.2 Build 25022327 (Latest)
Operating System: macOS Sequoia 15.3.1 (Latest)
Browser (if using Office on the web): N/A

The expected behavior is that Office.context.ui.displayDialogAsync consistently appends _host_Info (e.g., Outlook$Mac$16.00$nl-TR$telemetry$isDialog$$0) to the dialog URL across all machines, enabling messageParent to reliably communicate from the child dialog to the parent task pane. If &action=displayDialog is intentional, we expect messageParent to still work.

However, on some machines, &action=displayDialog is appended to the dialog URL instead of _host_Info. On these machines, messageParent never sends messages from the child dialog to the parent task pane—no errors are logged, and the parent callback isn’t triggered. On machines where _host_Info is used, messageParent works correctly. While &action=displayDialog correlates with the failure, we’re not certain it’s the direct cause—it could be a related symptom of an underlying issue.

To reproduce the issue, follow these steps:

Open a dialog to remote page:

const authUrl = '<url to authentication page>';
Office.context.ui.displayDialogAsync(authUrl, {
        height: resolution.y,
        width: resolution.x,
        displayInIframe: false,
        promptBeforeOpen: false,
    }, (result) => {
        if (result.status !== Office.AsyncResultStatus.Succeeded) {
            return;
        }

        let dialog = result.value;
        dialog.addEventHandler(Office.EventType.DialogMessageReceived, async (arg) => {
		console.log('Message received from child', arg);
        });
    });

Perform a few internal redirects and call messageParent() from authUrl:

Office.onReady(() => {
	Office.onReady(() => {
    Office.context.ui.messageParent(JSON.stringify({ message: "Hello" }), { targetOrigin: "*" });
});
})

On one Mac, the URL becomes https://?action=displayDialog, and no message is logged in the parent. On another identical setup, it becomes https://?_host_Info=..., and the message is received by the parent.

On Mac, messageParent fails when the dialog URL uses &action=displayDialog, but works with _host_Info.
On a failing machine + account combo, it always fails; on others, it always works.
Reproduction is rare and hard to debug, pointing to an environmental factor.
Outlook version/build is identical across machines, suggesting it’s not version-specific.
displayInIframe: true isn’t viable due to CSP/X-Frame-Options restrictions on the auth URL.

What triggers &action=displayDialog instead of _host_Info? Is it environmental (e.g., cache, account state), legacy behavior, or configurable?
Does &action=displayDialog directly break messageParent, or is it a symptom of a deeper issue?
Can we force _host_Info to ensure messageParent works?

Our Outlook add-in provides email encryption, requiring authentication via a remote website (Azure AD). This works across platforms, but on some Macs, messageParent fails, preventing authentication data from reaching the add-in. This blocks affected customers from using the service, and the inconsistency undermines reliability.

In conclusion, the issue of messageParent failing on some Macs, potentially linked to &action=displayDialog vs. _host_Info, is a complex problem that requires further investigation. We need to determine the root cause of this issue and explore possible solutions to ensure that messageParent works reliably across all machines. By understanding the environmental factors, legacy behavior, and configurability of this issue, we can develop a plan to address it and provide a better experience for our users.

Based on the information provided, here are some recommendations:

Investigate environmental factors: We need to explore the environmental factors that contribute to this issue, such as cache, account state, and machine configuration.
Analyze legacy behavior: We should analyze the legacy behavior of Office.context.ui.displayDialogAsync to understand why &action=displayDialog is used instead of _host_Info on some machines.
Explore configurability: We need to explore the configurability of this issue to determine if it can be resolved by changing the configuration of the add-in or the machine.
Develop a plan to address the issue: Based on the findings from the above steps, we should develop a plan to address the issue and ensure that messageParent works reliably across all machines.

By following these recommendations, we can develop a comprehensive plan to address the issue of messageParent failing on some Macs, potentially linked to &action=displayDialog vs. _host_Info.
Outlook on Mac: messageParent Fails on Some Machines, Potentially Linked to &action=displayDialog vs. _host_Info

Q: What is the issue with messageParent on Mac? A: The issue is that messageParent fails to send messages from the child dialog to the parent task pane on some Macs. This is potentially linked to the use of &action=displayDialog instead of the expected _host_Info in the dialog URL.

Q: What triggers &action=displayDialog instead of _host_Info? A: We are unsure what triggers &action=displayDialog instead of _host_Info. It could be an environmental factor, legacy behavior, or a configurable setting.

Q: Does &action=displayDialog directly break messageParent, or is it a symptom of a deeper issue? A: We are not certain if &action=displayDialog directly breaks messageParent or if it is a symptom of a deeper issue.

Q: Can we force _host_Info to ensure messageParent works? A: We are exploring the possibility of forcing _host_Info to ensure messageParent works. However, we need to determine the root cause of the issue before we can implement a solution.

Q: What is the expected behavior of Office.context.ui.displayDialogAsync? A: The expected behavior of Office.context.ui.displayDialogAsync is that it consistently appends _host_Info to the dialog URL across all machines, enabling messageParent to reliably communicate from the child dialog to the parent task pane.

Q: What is the current behavior of Office.context.ui.displayDialogAsync? A: The current behavior of Office.context.ui.displayDialogAsync is that it appends &action=displayDialog to the dialog URL on some machines, causing messageParent to fail.

Q: How can we reproduce the issue? A: To reproduce the issue, follow these steps:

Open a dialog to remote page:

const authUrl = '<url to authentication page>';
Office.context.ui.displayDialogAsync(authUrl, {
        height: resolution.y,
        width: resolution.x,
        displayInIframe: false,
        promptBeforeOpen: false,
    }, (result) => {
        if (result.status !== Office.AsyncResultStatus.Succeeded) {
            return;
        }

        let dialog = result.value;
        dialog.addEventHandler(Office.EventType.DialogMessageReceived, async (arg) => {
		console.log('Message received from child', arg);
        });
    });

Perform a few internal redirects and call messageParent() from authUrl:

Office.onReady(() => {
	Office.onReady(() => {
    Office.context.ui.messageParent(JSON.stringify({ message: "Hello" }), { targetOrigin: "*" });
});
})

On one Mac, the URL becomes https://?action=displayDialog, and no message is logged in the parent. On another identical setup, it becomes https://?_host_Info=..., and the message is received by the parent.

Q: What are the additional details about the issue? A: Here are the additional details about the issue:

On Mac, messageParent fails when the dialog URL uses &action=displayDialog, but works with _host_Info.
On a failing machine + account combo, it always fails; on others, it always works.
Reproduction is rare and hard to debug, pointing to an environmental factor.
Outlook version/build is identical across machines, suggesting it’s not version-specific.
displayInIframe: true isn’t viable due to CSP/X-Frame-Options restrictions on the auth URL.

Q: What is the context of the issue? A: Our Outlook add-in provides email encryption, requiring authentication via a remote website (Azure AD). This works across platforms, but on some Macs, messageParent fails, preventing authentication data from reaching the add-in. This blocks affected customers from using the service, and the inconsistency undermines reliability.

Q: What are the recommendations for addressing the issue? A: Here are the recommendations for addressing the issue:

Investigate environmental factors: We need to explore the environmental factors that contribute to this issue, such as cache, account state, and machine configuration.
Analyze legacy behavior: We should analyze the legacy behavior of Office.context.ui.displayDialogAsync to understand why &action=displayDialog is used instead of _host_Info on some machines.
Explore configurability: We need to explore the configurability of this issue to determine if it can be resolved by changing the configuration of the add-in or the machine.
Develop a plan to address the issue: Based on the findings from the above steps, we should develop a plan to address the issue and ensure that messageParent works reliably across all machines.