unless I'm missing something, the only time an insert should fail is if there is a MySQL error.
On a Dreamweaver or DataAssist insert behavior the line that actaully connects to the database and performs the insert is:
$Result1 = mysql_query($insertSQL, $test) or die(mysql_error());
this basically says to run the insert query, and die() (or stop executing the script) if an error occurs. If the email behavior is after the insert behavior, it will not have a chance to execute once the insert fails.
is there another instance where your insert is failing besides an error?