Do you run your owncloud server on your own hardware or in the cloud? Also I assume you use it pretty extensively so the files you are sharing would likely alr

Do you run your owncloud server on your own hardware or in the cloud? Also I assume you use it pretty extensively so the files you are sharing would likely already be there / not have to be uploaded first? On your own hardware with TLS and a decent password seems like a decent effort to me - better than just attaching things to an email :-) Exchanging the password might be tricky though...