OUTLOOK 2010: SendTo Mail Recipient not working on Windows 10
Ensure Outlook is set as the default Mail client
For 32 bit versions of Outlook…
Delete Msmapi32.dll located C:Program Files (x86)Common FilessystemMSMAPI1033
For 64 bit versions of Outlook… (I think this is the right path??)
Delete Msmapi32.dll located C:Program FilesCommon FilessystemMSMAPI1033
Open Outlook (Outlook will replace & register the Msmapi32.dll and then open).
Try the "Send To > Mail Recipient" again.