I'm not sure if there's more to this e-mail that you're not showing, but you're sending it as a multi-part message, but I don't see the boundary separator that sets this part of the e-mail to HTML. That may be part of the problem, because GMail and Yahoo may be forgiving the missing Content type declaration, and Outlook may be more picky... I'm really not sure. Check the PHP Mail function for some good examples of how to format that.
The thing I really thing is causing your problem is that you're missing a closing </td> tag after "Service Name". I always format my code so the HTML is very readable like this:
$email_message .= '<br/><br/>We have received new Data, please find the details below.<br><br>';
$email_message .= '<table border="0"">';
$email_message .= "<tr><td align='right'><b>Data Source Name\t\t : </b></td><td align='right'>$data_source_name</td></tr>";
$email_message .= "<tr><td align='right'><b>Report Month\t\t : </b></td><td align='right'>$report_month-$report_year</td></tr>";
$email_message .= "<tr><td align='right'><b>Date Received\t\t :</b></td><td align='right'>$date_received</td></tr>";
$email_message .= "<tr><td align='right'><b>Operator name\t\t : </b></td><td align='right'>{$oper_name[$m]}</td></tr>";
$email_message .= "<tr><td align='right'><b>Service Name\t\t :</b></td><td align='right'>{$serv_name[$m]}</td></tr>";
$email_message .= "<tr><td align='right'><b>Downloads\t\t : </b></td><td align='right'>{$download_ser[$m]}</td></tr>";
$email_message .= "<tr><td align='right'><b>Records\t\t : </b></td><td align='right'>{$row_serv[$m]}</td></tr>";
$email_message .= "<tr><td align='right'><b>Report Received TAT\t\t : <b></td><td align='right'>{$total_day['both']}</td></tr>";
$email_message .= '<table><br/>';
It makes it easier to catch those kind of errors. Also, if you're going to use double quotes, you may as well leave your variables inside the quotes because the server is going to have to scan the whole quote to find the variable, and it makes the code a little easier to read. IMHO.
Hope that helps!
Brian