Type about:preferences#applications<enter> in the address bar. Look for mailto and press the button to its right.

Outlook is selected in the mailto line but it still doesn't work and open outlook when an e-mail link is selected -unlike IE11which works perfectly for some reason

Very odd.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Yes the problem is still there starting in safe mode, looks like I'll just have to copy the links, then open outlook and paste into the address bar! I just think it's strange that IE11 doesn't have this issue, does firefox have some kind of compatibility issue with outlook 2010?

Ask you question here also;

https://support.microsoft.com http://answers.microsoft.com/en-US/windows/forum/windows_10

I have this problem too.

On my Windows 7 machine, where Windows Live Mail is my default mail program, Firefox 53.0 does open Live Mail correctly

On my Windows 10 machine, where MS Outlook 2016 is my default mail client Firefox does not open the email program. Yes, I checked in my options and Outlook is the default application for mailto

Very vexing.

Does anyone have a solution??

dmcentee said

On my Windows 10 machine, where MS Outlook 2016 is my default mail client Firefox does not open the email program. Yes, I checked in my options and Outlook is the default application for mailto

I have to start by saying that Windows 10 has some odd behaviors when it comes to default applications, and Firefox can't always work around them.

If you paste the following into the Windows search box or the Windows Run dialog and press Enter to submit it, does it launch a new message in Outlook?

mailto:someone@example.com?subject=Hello

Could you change your mailto setting on the Options page, Applications panel, to "Always Ask" and see whether Firefox displays a dialog with mail client choices when you click a link or when you paste the above into the address bar and press Enter to load it?

Thank you for your reply.

I changed mailto to 'always ask' --- and Firefox did as it was supposed to.

I changed mailto back to Outlook 2016 --- and presto, it works now.

I don't get it, but it appears to be fixed.

Thanks again.

p.s. I really, really dislike Windows 10. It seems like its raison d'être seems to be to force people to the 'store'. As far as I can see, it has not other value

dmcentee said

I don't get it, but it appears to be fixed.

The file that stores preferences set on the Options page, Applications panel sometimes becomes corrupted, and that probably straightened it out.