Fix test logic in is_usable_as_tmp_dir()

src/fmail.c

@@ -434,9 +434,9 @@ is_usable_as_tmp_dir(const char *dirname)
     if ( stat(dirname, &st_buf) != -1 )
         if ( S_ISDIR(st_buf.st_mode) )
             if ( access(dirname, R_OK | W_OK) != -1 )
-                return 0;
+                return 1;
 
-    return -1;
+    return 0;
 }
 
 static const char *