You can, but you will need an EFIN.

If you're not a tax professional, you really shouldn't be using any professional tax software because (1) these programs, by design, generally require much more technical knowledge to operate and (2) you will not be able to e-file any return, not even your own, without an EFIN, which the IRS only issues to tax professionals who apply for it through an extensive process.

ok thanks.  I am retired, but have continued to use proconnect which I am comfortable with.,'

You are indicating that it is not possible to send without EFIN.

Too late to apply for this year so I will just mail in.

Will check with Intuit if I should migrate to another product (e.g., TurboTax) if I would allow me to send via efile.

Start the EFIN process now so that you are ready to go in the future. https://www.irs.gov/e-file-providers/become-an-authorized-e-file-provider