Do you get the same issue using the built-in feature? To access that, you can use either:

• File menu (tap the Alt key to activate the classic menu bar) > Email Link

• Email Link button (might be in the unused buttons you can add using the Customize dialog, see: Customize Firefox controls, buttons and toolbars)

In case you have multiple "handlers" set up for Office 365 -- assuming that is your preferred email -- you might need to select a different one in the Options dialog. This article has the steps for that: Change the program used to open email links.

Any improvement?

Using the built in feature yields the same result. I checked the mailto option - it says TWINUI, whatever that is...I tried to browse and go to outlook, but it didn't work for me. Many thanks.

Found something called search and apps. Changed the mail programme in there. Yes!

Just have to find out how to kill Bing search now...

Many thanks

When I search for info on TWINUI it seems to be a PDF viewer, which is not a logical email client at all... The settings file that stores your application/download preferences might be corrupted. The standard recommendation in that case is to remove the file and have Firefox rebuild it. (You may need to re-enter your preferred handlers for PDFs or other types of downloads.) Here's how:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename mimeTypes.rdf to mimeTypes.old.

Start Firefox back up again. (To re-open windows and tabs from your previous non-private session, you can use the History menu.)

Firefox now should detect your default mail application at the Windows level and set that as your preference. Any improvement?

Oh, was that solved already?

What's the issue with Bing? If it's showing up on new tabs... Here's how you can change your new tab page:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter your preferred page:

• Page thumbnails (default) => about:newtab
• Blank tab => about:blank
• Built-in Firefox home page => about:home
• Any other page => full URL to the page

Press Ctrl+t to open a new tab and verify that it worked. Fixed?

If problems persist, some potential diagnoses and remedies:

If Firefox won't let you edit this setting: you may have something called SearchProtect on your system. This needs to be removed from the Windows Control Panel.

If Firefox lets you save your change but ignores it: one of your extensions may be overriding it. You can review, disable, and/or remove extensions on the add-ons page. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then cast a critical eye over the list on the right and disable (or remove) anything unknown.

If the change works during your session, but at the next startup is back to the unwanted page: you might have a user.js file in your personal Firefox settings folder (your Firefox profile folder). This article describes how to track down and remove the file: How to fix preferences that won't save.

Any luck?