Emesene is widely considered best of breed of the multiplatform IM clients for the WLM protocol.
For daily use I prefer a single multiprotocol IM client such as Pidgin. I find it handy to have all my IM accounts open in a single interface. Multiprotocol clients frequently do not implement every obscure feature of every protocol, however, which can leave me hanging when I happen to need one of those features.
Emesene to the rescue. It only does the WLM protocol, but it does it completely. It isn’t my daily driver, but it is the tool I use when the multiprotocol clients let me down.
Another use of Emesene is as a drop-in replacement on Windows for Microsoft’s official WLM client. Unlike the official client, Emesene is open source and lightweight.
Emesene has lots of plugins.
MANAGING CONTACT ALLOW AND BLOCK LISTS
In Options – Preferences – Privacy, adjust the Allow and Block lists as desired, just like in the official WLM client.
Is Emesene not what you’re looking for? There are many other IM clients for Linux available.