Without it, nothing will work via RSS and you don’t want to submint an invalid feed to iTunes. ┬áHere are some sites to help.

Dave Jackson from the School of Podcastng

http://schoolofpodcasting.com/the-27-steps-to-get-your-podcast-into-itunes/  Step 26

 

Because Apple Says you do!

https://www.apple.com/itunes/podcasts/specs.html