This might be a complicated way of doing this but you could do two SQL queries. One to find the last unique id and then the next to search for the rest of the details under that ID number:
// Replace the word "unique_id" with whatever your id label is for that column.
$query = "SELECT MAX(unique_id) FROM newsletters LIMIT 1";
$result = mysql_query ($query);
$row = mysql_fetch_array ($result);
$query2 = "SELECT * FROM newsletters WHERE unique_id = '$row[unique_id]'";
$result2 = mysql_query ($query2);
There may be a way of doing it using only one query but hey, this will work.