I've come across something a bit strange I was hoping someone with more experience with Paypal can explain, Specifically the IPN feature.

It seems I'm getting two very different hits to my IPN listener. The first one always fails, The second one passes.

Now I know Paypal tends to send duplicates, But what I've noticed is two very different $_POST arrays being recieved.

Here's the respones :

    [2014-06-08 23:51:19] 
    RAW POST DATA : Array
    (
            [transaction] => Array
            (
                    [0] => ILS 20.00
            )

            [payment_request_date] => Sun Jun 08 13:52:12 PDT 2014
            [return_url] => MY_URL
            [fees_payer] => EACHRECEIVER
            [ipn_notification_url] => MY_URL
            [sender_email] => [email protected] //fake email
            [verify_sign] => ANp5TpLat3.2ylx.cECtVZ..5HejAsVcs05tdVC7RldmeYNJ91SKaqFJ
            [test_ipn] => 1
            [cancel_url] => MY_URL
            [pay_key] => AP-04B74091M7083584A
            [action_type] => PAY
            [transaction_type] => Adaptive Payment PAY
            [tracking_id] => 13 // This is a number I passed, But it doesn't exist in the 2nd POST
            [status] => COMPLETED
            [log_default_shipping_address_in_transaction] => false
            [charset] => windows-1252
            [notify_version] => UNVERSIONED
            [reverse_all_parallel_payments_on_error] => false
    )

    [2014-06-08 23:51:19]
    RAW POST DATA :  Array
    (
            [transaction_subject] =>
            [payment_date] => 13:52:28 Jun 08, 2014 PDT
            [txn_type] => web_accept
            [last_name] => test
            [residence_country] => US
            [item_name] =>
            ....

            (this continues for quite a bit more)

            ....
            [payment_fee] =>
            [mc_fee] => 1.78
            [mc_gross] => 20.00
            [custom] =>
            [charset] => windows-1252
            [notify_version] => 3.8
            [ipn_track_id] => f93ce8bdd4382
    )

My problem
The first IPN with the juicy tracking_id fails, the 2nd IPN is verified, But once the IPN is verified I no longer have access to the tracking_id.

My questions Why does paypal send two different IPN's
Why are they different?
Why isn't any of this documented on Paypal? :(