the good answer is the 2)
The TA are shipped with the app suite.
They are specific per version and server type and are stored in the folder Splunk_for_Exchange\appserver\addons\ (example TA-Exchange-2010-MailboxStore)
You have to untar/unzip the installer, extract the TA you need from the folder, then copy them to the correct server in the %SPLUNK_HOME%\etc\apps\ folder from the forwarders.
... View more