What is wrong in this line
$Date = SUBDATE(NOW(),1) $mailBody = 'Please find details of Accounts Created As On ' .$Date;
If you want to get yesterday's date in PHP try the following:
$date = date('d.m.Y',strtotime("-1 days"));
What is the error you're receiving and where is that code?
I'm a bit confused as the variable seems PHP but "SUBDATE(NOW(),1)" seems like (part of) a MySQL query.
If you want to run MySQL queries against the db you can use DBManagerFactory, see the following guide:
Retrieving data ...