Caramail is a famous (at least here) free mail account hosting service. Today its mailer daemon sent me that:

Command died with status 1: "/usr/sbin/mail.local".
Command output: xmlrpc_client.c:185: assertion failed

It's rather strange to involve an heavywight protocol for mail delivery. And it's even more troubling that the delivery fails because of that. I'm wondering what they are doing with it...