Conversations Classic works with every XMPP server out there. However XMPP is an extensible protocol. These extensions are standardized as well in so called XEP’s. Conversations Classic supports a couple of those to make the overall user experience better. There is a chance that your current XMPP server does not support these extensions. Therefore to get the most out of Conversations Classic you should consider either switching to an XMPP server that does or - even better - run your own XMPP server for you and your friends.
* XEP-0280: Message Carbons which automatically syncs the messages you send to your desktop client and thus allows you to switch seamlessly from your mobile client to your desktop client and back within one conversation.
* XEP-0308: Last Message Correction allows you to edit last message as well as retract it.
* XEP-0313: Message Archive Management synchronize message history with the server. Catch up with messages that were sent while Conversations Classic was offline.
* XEP-0352: Client State Indication lets the server know whether or not Conversations Classic is in the background. Allows the server to save bandwidth by withholding unimportant packages.