how very senior citizens can file their income tax return without physically going to the IT office ?

there are a very large no of income tax payers who prepare their returns all by themselves .The amount of tax is small or it may be even nil in some cases.If it is sent by registered post, the acknowledgement form is not received back.
If it is submitted electronically, there is the question of digital signature,( to subscribe to a digital signature is a costly proposition). In these days of electronics how it can be done in a proper way ?

The answer is to be on the Indian context