Use of Drop Box if one of the applicants is less than 60

My parents are in the process of applying for a Visitor visa at chennai. My dad is over 60 years but my mom is not. They wud be applying together. So can they both use the drop box or only my dad can?

Thanks
Swami

my parents same case i took appointment and sent both of them o chennai they attended on 29th and got 10 years visa .

only the one who's age is => 60 is qualified for the DropBox. The person can still avail Interview by setting up an appointment. If they want to go together setup interview for both.