To set Chrome, Edge, or Firefox as default mail client for mailto links (mailto handlers) requires several steps. In managed environments, this can be done for all three browsers with Group Policy.
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Many organizations prefer the browser as their mail front end because it requires no software installation and is available on virtually all devices. Microsoft is also increasingly reliant on the web app with Office 365, and the new Outlook is based on web technology.

When using a web-based mail system, users expect the mail app to open in the browser when they click a mailto link on websites. By default, however, they see the mail app that is shipped with Windows, even when they don't have an account set up in this program.

Set a browser as the default for mail

Redirecting the mailto handler to a web mailer involves the following steps:

  • Register the mail app in the browser.
  • Set the mail client as the default within that browser.
  • Configure the browser as the default program for the mailto protocol.

This process is identical regardless of whether users perform this task interactively or whether admins use group policies to do so.

Interactive configuration

Whether it's Chrome, Edge, or Firefox, registering a mail application as a potential mailto handler starts with opening the mail app in the browser. Most web mailers signal the browser that they want to be registered as a mail program. Users then receive a notice to that effect.

For Chromium-based products, an icon then appears in the address bar. Clicking on it opens a dialog box in which you can choose from Allow, Deny, and Ignore. If you choose Allow, the application registers itself as a mailto handler.

Google Chrome indicates that outlook.com wants to register as a mail program

Google Chrome indicates that outlook.com wants to register as a mail program

Firefox displays a bar with a corresponding request. Clicking the Add application button registers it as a mail application.

Firefox offers to register the mail application

Firefox offers to register the mail application

The next step is to set the application as the default within the browser if there is more than one.

In Google Chrome, go to Privacy and security > Website settings > Additional permissions > Protocol handlers. In Edge, you can find the list of registered applications under Cookies and site permissions > Site permissions > Protocol handlers.

Selecting the default mail application within the browser

Selecting the default mail application within the browser

There, click the More Options button (three dots) next to the preferred mail application, and select Set as default. You can also remove entries that are no longer needed here.

In Firefox, you can find the corresponding selection under General > Applications > mailto. Gmail and Yahoo Mail are already set there, but the browser also shows the mail services that you have registered elsewhere.

Programs eligible to be mailto handlers in Firefox

Programs eligible to be mailto handlers in Firefox

Set a default app in Windows

If you have set your preferred mail application as the default in the browser and then click a mail link on a website, the Windows mail app will still continue to start. To change this, you must also set the default program for email in the operating system.

To do so, open the Settings app, go to Apps > Default apps, and look for "mailto". Clicking this entry opens a list of programs that can be used as the default for this protocol. Select the browser you want to use for web mail, and click Set default.

Selecting the default program for mail in the Settings app

Selecting the default program for mail in the Settings app

Before clicking a mail link to test the configuration, restart Chromium-based browsers.

Set default mail client via Group Policy

All three browsers offer the option to configure the mailto protocol via GPO as well. The corresponding setting not only allows you to register an application, but also to set it as the default right away. It exists for all three under both the computer and user configurations.

For Chrome and Edge, it is called Register protocol handler and can be found in the Default Settings branch under Content settings. Activate this setting and enter a configuration in JSON format. For Gmail, the data looks like this:

[ { "url": "https://mail.google.com/mail/?extsrc=mailto&url=%s", "default": true, "protocol": "mailto" } ]

The biggest hurdle here is finding the correct URL for the service in question. For Office 365 OWA, the following should work:

https://outlook.office.com/owa/?&rru=compose&to=%s

Register the mailto protocol handler in group policies for Chrome

Register the mailto protocol handler in group policies for Chrome

In Firefox, the setting in question is located in the root directory and is called Handlers. The documentation also includes the configuration of Gmail as an example.

Configure the mailto protocol handler for Firefox using group policies

Configure the mailto protocol handler for Firefox using group policies

As with the manual configuration, when managing the mailto protocol using Group Policy, you must ensure that the desired browser is configured as the default at the Windows level. This is done as described above via the Settings app. This configuration can then be exported using DISM and distributed using a GPO.

Summary

If you want to set a web-based application as the default for mailto links instead of the mail app included in Windows, you must first register it in the desired browser and set it as the default there. Then, enter the browser as the default app for the mailto protocol at the Windows level.

This process can also be controlled centrally via group policies. Chrome, Edge, and Firefox all offer a corresponding setting. This expects input in JSON format, whereby the admin determines the required URL in the documentation of the mail service.

1 Comment
  1. bgavin 4 weeks ago

    Thanks!
    Much appreciated.

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