Well, IRC sorta as it does group chats. But email? Is there an XEP for that? XMPP can probably gateway to/from email, but XMPP can gateway to pretty much everything in the known universe...

An Email is a message with a subject line and potentially attachments. XMPP has the former in the core, can do the latter with XEP-231 (https://xmpp.org/extensions/xep-0231.html). A message can have one or multiple recipients, just like an XMPP message.

Email is really a simple form of messaging, where you put some content and expect the chain to route it to your destination; pretty much any IM system can emulate it, and XMPP goes a little bit beyond in providing the bits that different an email message from an IM message.