Not able to launch msn using url schema

I want to launch MSN through my iphone App. I am using url shema-

BOOL msn = [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"msnim://"]];
if (msn) {
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"msnim://"]];
}
else {

    UIAlertView * errorAlert = [[UIAlertView alloc] initWithTitle: @"MSN not Installed" message: nil delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; 
    [er开发者_高级运维rorAlert show];  
    [errorAlert release];

but its not working. Am i using wrong custom url for MSN???? If yes,then what is the url scheme for MSN.