Email to let my landlord we are leaving

The problem is that you need to proove your landlord/landlady has well received your 3 months termination notice on time. Therefore lots of tenants doesn't use email because you have no proof that your landlord has reveived the email.
In Belgium, it is very common to send a registered letter with proof of receipt to break any contract.
For rental contract, there are plenty of templates available on the Internet, that you can download for free.
You fill it, sign it (husband AND wife) and send it via a registered letter with proof of receipt.
You can even do that in any Delhaize