You can use this website (
https://send.djazz.se ) to send books wirelessly to your kobo. You have to open it in both your Libra and computer/phone, put the same code in both sides and then upload/download the book. Not as easy as sending them by e-mail but fairly straightforward.
If you use Calibre you can also access your calibre content server with the browser to download your books wirelessly.