Issue: RSS Email body shows html tags like this <p>

Fix: Need to use Custom RSS Item element in the email builder, and instead of using {{rss_item.content}} use {{{rss_item.content}}}

HTML Based RSS Feed

The values returned by the RSS-based custom variable {{rss_item.title}} are HTML-escaped. For example, if the expression contains &, then the returned HTML-escaped output is generated as &amp; or if your RSS Feed has HTML-based text instead of plain text then it will be rendered as plain text.
If you don't want it to escape a value, use the "triple-stash", {{{:
Eg: if your RSS feed source is something like this
without "triple-stash" it will render like this
once you will use "triple-stash" {{{rss_item.content}}} it will render like this