+2  A: 

What about using double-quotes arround your values, and using real newlines, like this :

message = "Hi {0},

This is a test message.
Goodbye!"


As an example, using this portion of code :

$config = new Zend_Config_Ini(APPLICATION_PATH . '/config/application.ini');
var_dump($config->production->testmessage);
die;

With application.ini containing this :

[production]

testmessage = "this is
a new
message"

I get the following output from my var_dump :

string(21) "this is
a new
message"
Pascal MARTIN
Thanks, that worked great.
Nick