How to get output port name for builtin Delay block?

simBlockH = get_param(target_module, 'Handle');
handles = find_system(simBlockH, 'LookUnderMasks', 'on', 'FollowLinks', 'on', 'SearchDepth', 1, 'BlockType', 'Outport');
portNames = cellstr(get_param(handles, 'Name'));

I am successfully using the above code to get the output port names for my blocks.

However, I tried the above code to get the output port name for a builtin Delay block I am using, but failed. How can I do that?