What I already found is
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@\"mailto:\"]];
But I just want to open the Mail ap
Apparently Mail application supports 2nd url scheme - message:// which ( I suppose) allows to open specific message if it was fetched by the application. If you do not provide message url it will just open mail application:
NSURL* mailURL = [NSURL URLWithString:@"message://"];
if ([[UIApplication sharedApplication] canOpenURL:mailURL]) {
[[UIApplication sharedApplication] openURL:mailURL];
}