Suppose my Skype integration wants to filter notifications for a user to messages that contain the string "server down". Is this possible?
Per default Skype for Business (=SfB) can only block URL or attachments as written here. Maybe there exist an 3rd party application which can do that, but I do not think so. Reason: The problem here is that SfB can perform peer2peer connections (see more here). That means if you and your workmade are in the same network and no firewall restricts you both and you both perform a chat together, the chat is done between both of you (without a real server connection; for more infos see the official documentation inside the 2nd link). So a 3rd party software (which might sitting on the server) will not capture that kind of information. So what you might need is a client software on every PC. But what about the mobile clients then? So I do not think that such a software exists or would be possible to build.