As part of our ongoing virtualization efforts, we rolled out an upgraded version of our mail relay server yesterday at noon. Unbeknownst to us, the default value for a configuration variable changed in a subtle way that affected delivery to some subdomains. This definitely affected delivery to some of our email lists. We put a temporary workaround in place earlier today and, after some research, put a permanent solution in place around 9pm. We are continuing to monitor the flow of email and everything is now looking good. If you continue to notice any delivery delays or problems, please email firstname.lastname@example.org and we will investigate.