For instant messaging, I’ve been using Trillian for years. A great product, but lately (being the last few months), there are some problems with sending messages.
With the different messaging services changing their protocols, I thought that was the reason, but it only seems to occur when initiating a chat session and then not even every time. After setting up a packet scanner, I noticed that the messages didn’t even get sent. So the problem is not the network, but Trillian.