Is it legal to give notice that I will be vacating my rental via e-mail?

I'm not certain that is sufficient. If your landlord accepts that then your fine, but I wo uld follow up with letter via postal service. Please also double check what is indicated in your lease. It may require that you do it via USPS.

Spend the 42 cents and mail it instead. Emails have a bad habit of getting deleted without being read.