Doesn't the current Copy/Paste feature work for you ?
Of course, the result depends on how 'smart' the receiving end is.
If you paste a whole artboard's content in Adobe Illustrator, all elements will be separately editable.
If you're working in an email application, the pasted content will be one large pixel image, because the mail content doesn't understand nor support the construction of all elements within.
So your mileage will vary...
I've just tried to copy and paste between Xd and an email, it worked fine so you should be able to do that. Select the artboard, or the contents, then either use the right click dropdown to select copy then paste or Ctrl(win) C & Ctrl(win) V to copy and paste with keyboard shortcuts. All these options worked for me.