It is email as a support channel. Mail sent to your support address becomes a conversation in ZChat, threaded, attributed to the sender, and answerable with the reply-by-email action your agents already use.
The free edition is not omnichannel. Email is the free channel beyond the website widget. WhatsApp, SMS, Facebook Messenger, Instagram, Telegram, LINE and API inboxes are part of Premium, at $19 per agent per month, as are voice calls through your own Twilio number.
It is not a mailbox poller. ZChat doesn't hold your mail credentials or log in to check for new messages. Your mail server - Postfix, Exim, an internal relay, whatever you already run - passes the message to ZChat when it arrives.