Podomatic does not have a user interface from which to set up a 301 redirect. Therefore, to migrate your feed, you must email Podomatic at care@podomatic.com asking them to set up a 301 redirect from your Podomatic RSS feed to your RSS.com feed.

Here is an email template that you can use:

Hi Podomatic Support, 

I'm moving my podcast to a new host provider and kindly request that you apply a redirect for the following show (Insert Your Podomatic Feed Here)

Can you please apply a 301 redirect to my new RSS.com feed at (insert your RSS feed here, for example, https://media.rss.com/myRSSfeed/feed.xml)

Please let me know if you need any more information

Thanks in advance.