• Clean Windows 10 home edition installed
• Office 365 installed
• Open Outlook and configure profile using local pst file
• Run either 32/64 bit executable that calls MAPIInitialize
• A dialog box gets displayed saying that there is no default mail client, but Outlook is the default mail client. The function always returns E_FAIL.

Hi,

As you mentioned "MAPIInitialize", I need to confirm, do you use the program written by yourself? Or a program from a 3rd-party? Let me know what it is then I can decide what the next step is.

Regards,

Melon Chen
TechNet Community Su

Yes it is a program written by myself. It works perfectly on all previous windows versions.

Hi,

Please try the Process Monitor tool to monitor what is possibly denied during the MAPIInitialize process, which may cause the issue.

Regards,

Melon Chen
TechNet Community Su