Windows OS has a long running issue when it comes to using 'Send to' > 'Mail Recipient' or 'Send to' > 'Thunderbird' It's not worked for me for ages. Microsoft help forum sites have tons of reports on this going back years. If I have an image file and use : 'Send to' > 'Mail Recipient' - nothing happens 'Send to' > 'Thunderbird' - Windows OS chooses to open it in Photos and nothing is added to email. Then Windows starts running hard because the fixmapi.exe file repeatedly is invoked. I can see ti in the Task Manager. I have to reboot the computer to disable it. I just create email and add attachment because I know it works every time. Less frustrating, But you could try this which did work for one person: ''Set winword to run as administrator then reset winword so as NOT to run as administrator. And after I did that, I no longer got the MAPI failure. '' But if using a 'share' option - it's been reported that 'word' only shares to 'outlook', MS has control over this.