TypePad AntiSpam is a plugin that integrates WordPress blogs with Six Apart's spam blocking service.
I did receive the following message from TypePad:
We recently contacted you to let you know that we are retiring Typepad Anti-Spam on March 1st and transitioning you to Impermium (http://impermium.com) for your anti-spam needs.
The switch will take place on March 1, 2013. This will be a seamless transaction on your end since we'll automatically switch your requests to Impermium. There's nothing for you to change.
It's now March 10th. It was seamless. Spam continues to be caught. I'm pleased with this plugin.