Insert contact error

This is giving error. (You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@myemail.net' at line 1)

$user_id = $_SESSION['user_id'];

    $emails = $_REQUEST['emails'];
                $subject = "Invitation from $email";
                $headers = 'From: '.$email;
                $emails = $_REQUEST['emails'];
                foreach ($emails as $to) {
                    list($to,$name) = split(':::',$to,2);
                    $message = "Hi $name, $email would like you to take a look at this site! http://www.lunarsys.com\r\n\r\n";
                    mail($to, $subject, $message, $headers);
                    echo "Mail sent to $name ($to)<br/>\r\n";



    $query = "SELECT j_user_id FROM jt_members_external_contacts WHERE j_user_id = $user_id AND contact_email = $to;";

    $result = mysql_query($query) or die(mysql_error());

    $conrows = mysql_num_rows($result);

    if($conrows > 0)
    {

        echo "Exist";   
    }else
    {


                    //

    //Insert News into Articles Database
    $sql_insert = "INSERT into `jt_members_external_contacts`
                (`j_user_id`,`contact_email`,`firstname`
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                VALUES
                ('$user_id','$to','$name'
                )
                ";

    mysql_query($sql_insert) or die(header("Location: /error_page?error_msg=1"));
                }

replace this line:

$query = "SELECT j_user_id FROM jt_members_external_contacts WHERE j_user_id = $user_id AND contact_email = $to;";

with this:

$query = "SELECT j_user_id FROM jt_members_external_contacts WHERE j_user_id = $user_id AND contact_email = '$to'";

There should be quotes around $to:

 $query = "SELECT j_user_id FROM jt_members_external_contacts WHERE j_user_id = $user_id AND contact_email = '$to';";

By the way - if this is your actual source code, don't forget to properly escape the user input $_REQUEST['emails'];, because as it stands this script has a serious SQL injection vulnerability where a specially crafted request parameter can compromise your database.

For example:

foreach ($emails as $to) {
    list($to,$name) = split(':::',$to,2);
    $to = mysql_escape_string($to);
    ...

This will also prevent valid email addresses like tim.o'brein@example.com breaking your script.