Not a plug-in but this does what you are asking for:
<?php
global $current_user;
get_currentuserinfo();
if ($current_user->user_level == 10 ) {
$query = "SELECT * from $wpdb->comments WHERE date(comment_date) >= date(now()-interval 30 day)";
echo "<h3>Email adddresses list</h3>";
$result = mysql_query($query) or die(mysql_error());
echo "<ul>";
while ($rowA = mysql_fetch_array($result)) {
echo "<li>".$rowA[comment_author_email]."</li>";
}
echo "</ul>";
// -----
echo "<h3>Email ready string</h3>";
$peeps = array();
$result2 = mysql_query($query) or die(mysql_error());
while ($rowB = mysql_fetch_array($result2)) {
$peeps[] = $rowB[comment_author_email];
}
$emailready = implode(', ', $peeps);
echo $emailready;
} else {
// nada
};
?>
It will create a list of all the emails of users who commented in the last 30 days. Under that it will then place all those emails into 1 line separated by commas so you can just copy and paste the whole this into your email client.
It will only show for the admin when they are signed in (since you shouldn’t make the list of emails public). Just add that to a page or something, run it, copy it and then delete it if you want.
