> It's tough finding an open-standards based IM application for corporate use.

I didn't try it, but this seems interesting: https://github.com/jesse-greathouse/eIRC

"eIRC is a modern, scalable enterprise messaging architecture built on the IRC protocol. Designed for organizations that require ephemeral, real-time communication without the heavy operational overhead of pub/sub systems like Apache Kafka, eIRC delivers high-throughput, low-latency chat experiences while minimizing memory and CPU usage per user."

It does support history as well: "IRC History Bridge: Implement Redis-backed buffer for message replay".