I have just set up my new Surface Studio running Windows 10 and have added my two Gmail accounts to the Mail app. Emails have been downloaded and I can send text emails with no problem from the Mail app. Sent emails are recorded in Sent Mail in the app, as well as in the Sent Mail folder in Gmail. The recipients have confirmed they've arrived. BUT if I add an attachment to an email, and press send, the email vanishes. There is no trace of it in the Drafts folder. Nor does it appear in the Sent Mail folder. And it never arrives. This only seems to happen when attachments are in the email.

Has anyone else experienced this? Can you recommend anything I can do to overcome this? The computer is brand new (arrived yesterday) and I have not entered any factory settings. I've added the two Gmail accounts using the functionality within Mail and haven't changed any settings. Does anyone have any suggestions how I can solve this strange blip and send attachments with no 'vanishing' problems? Thanks in advance!