diff --git a/arch/x86/scc/icc.c b/arch/x86/scc/icc.c
index 2cb97066..594b6ebb 100644
--- a/arch/x86/scc/icc.c
+++ b/arch/x86/scc/icc.c
@@ -232,8 +232,12 @@ int icc_ping(int ue)
 
 int icc_mail_ping( void )
 {
+	uint32_t flags;
 	int remote_rank = (my_ue+1)%2;
 	
+	// iRCCE is not thread save => disable interrupts
+	flags = irq_nested_disable();
+
 	// send mail
 	iRCCE_mail_send( 0, my_ue, 0, NULL, remote_rank );
 
@@ -246,6 +250,8 @@ int icc_mail_ping( void )
 	// show content	
 	iRCCE_mailbox_print_header( mail );
 	
+	irq_nested_enable(flags);
+	
 	return 0;
 
 }
diff --git a/kernel/main.c b/kernel/main.c
index ac65706f..38803cf9 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -115,7 +115,9 @@ int main(void)
 	sleep(5);
 	list_root();
 	test_init();
+	kprintf( "calling mailbox test ... \n" );
 	mailbox_test_init();
+	kprintf( "mailbox test succeded!\n" );
 	per_core(current_task)->status = TASK_IDLE;
 	reschedule();