Yesterday afternoon at approximately 4:45PM we completed the turn up and migration of services to a new set of geographically redundant proxy servers used by our internal mail infrastructure to communicate between the various clusters that support email services. Unfortunately one of the new proxies was left out of an ACL which prevented that proxy from being able to connect to the mail forwarding cluster. This resulted in about 50% of forwarded mail (typically configured in the “Forwarding” section of Sonic Member Tools) being rejected. These rejected messages would have resulted in non-deliverable messages being returned to the original sender instead of being delivered as intended.
We apologize for any issues this may have caused and will review our systems for any opportunities to improve monitoring to ensure that if something like this happens again it is immediately detected and resolved.