Using the TurboTax personal editions, only the current tax year 2018 tax return can be filed electronically. Prior year tax returns, including tax year 2016, can Only be printed and mailed to the IRS and/or a State.
Mail the returns to the IRS and use a tracking service from the US Post Office with a return receipt requested so that you will have proof the tax return was received by the IRS.
IRS website for mailing a tax return, with or without a payment, by state - https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
Or use a private delivery service such as UPS or FedEx. Go to this IRS website for the mailing address if you use a private delivery service - https://www.irs.gov/filing/submission-processing-center-street-addresses-for-private-delivery-servic...