Apple released its Mail Update for Mavericks on November 7, 2013. The update “improves stability and compatibility with Gmail, and includes fixes for users with custom Gmail settings.”
MsgFiler 3 owners will want to install MsgFiler Engine 1.1.6 to continue enjoying fast filing performance.
Original MsgFiler Mail Plugin owners will need to install version 2.2.1.
Whenever Apple releases an update to OS X or Mail, Mail plugins such as MsgFiler are routinely disabled. We usually have, however, either a beta or a new version of the MsgFiler Engine and Original MsgFiler Mail Plugin available. So, if you receive an error from Mail that one of the plugins have been disabled, visit the support pages to download the latest versions.