this code does not start a loop:
$row_rs_units = mysql_fetch_assoc($rs_units);{
You need to add another do { command:
<?php mysql_data_seek($rs_units, 0);
$row_rs_units = mysql_fetch_assoc($rs_units);
?>
<?php
do {
echo $row_rs_units['sec_email'].";"; ?>
<?php } while ($row_rs_units = mysql_fetch_assoc($rs_units)); ?>