You can use emojis in the chat using ":shortname:". The short name can start and/or end by a colon (:), and only contain alphanumerical characters, underscores and hyphens. It is strongly recommended to start them by a colon, so that users can use autocompletion (by typing ":" then press TAB).
If you are **not using the standard `5269` port**, you must also add a SRV record for `_xmpp-server._tcp.your_instance.tld.` (same as above, just without the `room.` prefix).Of course, you can also add this record if you use the standard port. It will also work.