Lotus Notes Mailto Issue: “Could not perform this operation because the default mail client is not properly installed.”

Exellent post from the University of Windsor.
All credits go to those guys!

 

Why do I get “Could not perform this operation because the default mail client is not properly installed” error message followed by dozens of blank Internet Explorer windows when I click on a mailto: link or a link in the Pure Message quarantined message digest?

It appears that after installing Internet Explorer 10 on a Windows 7 computer that had Lotus Notes or another mail client already installed, Internet Explorer 10 removes some registry entries that control what happens when a mailto: link is clicked. This results in the following error message:

Followed by dozens of blank Internet Explorer 10 windows.

To resolve the problem, you may run the following registry patch that will add the necessary Windows Registry keys back to the Windows Registry:

mailto.reg

Alternatively, you may uninstall Internet Explorer 10 by going to the Control Panel, selecting “Uninstall a Program” (if using the category view) or “Programs and Features” (if using the icon view), selecting “View installed Updates”, then selecting Microsoft Internet Explorer 10 and clicking uninstall.