We are currently facing issues with outgoing email messages on multiple servers which is causing all/most emails sent on those servers to result in an error. We are actively investigating the issue, and may be forced to reboot the server in order to be able to properly administrate it. We will keep you updated further through this thread. Thank you for your understanding and patience.
Apologise for the inconvenience caused. We are still working on this issue and making every effort to get this fixed as quickly as possible. We will keep further updates posted here.