In a single server 8.0.1 Network Edition installation, I have been unable to make changes to "Configure > Global Settings > Attachments > Currently blocked extensions by MTA" and have those changes stick. I can add the desired file types, see them listed in the "Currently blocked extensions by MTA" and then "Save," which shows a "Global Config is modified" popup with a green checkbox. All apparently goes fine, however, the changes do not seem to persist. If I leave the screen, and come back, "Currently blocked extensions by MTA" shows up as empty, and from a much more practical standpoint, it does not block the selected file types. I have tried restarting the server after making the changes, in case the MTA needed to restart for this to works, but that has not helped either.

Any advice or guidance would be greatly appreciated.