How to Sending emails from a Spreadsheet for non fixed(variable or floating) number of email

How to Sending emails from a Spreadsheet for non fixed(variable or
floating) number of email

the code i got it from & i ran the code as per the what the code indent to
run the problem it the code runs for fixed no of rows & column i want to
run it for any no of rows.It should take automatically based on the number
of rows without specifying it the code since in this code we need to
specify how number of rows to scanned & mailed to be send
Please help me if have any doubt please do sent you query to
rocketengg.88@gmail.com
For your ref
https://developers.google.com/apps-script/articles/sending_emails