With Office 365, the default mail client is not set to Outlook. It sounds like a simple issue, but after a long search for a solution, it ends with a surprise! All starts with using the Adobe Acrobat Reader function to send a PDF document through the default email client. However, the use ends with an error message that no default email client is available. The default email client is defined under the registry key HKLM\SOFTWARE\Clients\Mail
, but precisely that key is deleted when ending Outlook!