Dear Anshu,

Yes, your e aadhar card (not the letter) is acceptable in lieu of aadhar card for neet 2019which you can download it via your email and the password to open that email will be first four letters of your name and then the birth year (the instruction of  how to write the password will be mentioned) . Do get a colored print out of it. On a safer side carry other identity proof and their photocopy so that if in case they reject e aadhar card, you have another id proof to show to the authority.