My wife's W-2 lists the number 0 in box 15 (Employer State ID Number). It says my only option is to file by mail. Is there another way for me to still e-file??

It is okay to enter the employers federal ID number in place of the state ID number. The Employer’s federal ID number is located in box b of your W-2 form.  Your State Department of Revenue will be able to easily identify your employer from their 9-digit federal EIN.