outlookIf you’re running Microsoft Outlook you may have run into this error message. The Microsoft KB article says you can run into it when trying to send an email from a third party app. I’ve also read where Adobe Acrobat can cause it. For me, I’m running Windows 10 Technical Preview and Office 365. The “Either there is no default mail client or the current mail client cannot fulfill the messaging request. Please run Microsoft Outlook and set it as the default mail client.” error message would just randomly popup for me, even without trying to send an email.

There’s a Microsoft FixIt app you can use, but it doesn’t work if you’re running Windows 10 Technical Preview. Instead, you have to edit the registry, then run Office Repair:

– Click Start, and then click Run.
– In the Open box, type regedit, and then press ENTER.
– In Registry Editor, locate the following subkey in the registry:
HKEY_LOCAL_MACHINESoftwareClientsMailMicrosoft Outlook
– Select the subkey, and then press DELETE.
– Click Yes.
– Quit Registry Editor.
– Start Outlook.
– For Outlook 2000 and Outlook 2002, click the Help menu, and then click Detect and Repair .
– For Outlook 2007, click the Help menu, and then click Office Diagnostics .
– For Office 2010, Click Start, click Control Panel, click Programs and Features, select Microsoft Office 2010 and then click the Change button. Next, click Repair, and then click Continue.
– Follow the instructions on the screen to complete the repair.