We're happy to report that the problem has been resolved. As of this morning we are no longer seeing any bad DNS records. You may continue to hear reports of bounced mail for a few days as the return of those messages to the sender is decided by a local mail server policy, usually no more than 4 days.
Our DNS Registrar "accidentally" hijacked our domain last night causing ALL netgate.net names to point to bad IP addresses. Since everything (mail) utlimately resolves to a netgate.net hostname that caused mail delivery issues for everyone.
The issue has been corrected but there may be some bad records lingering in the Internet DNS servers and resolvers for a few more hours. You can clear your local resolver cache by rebooting your system. If your local DNS server (cable/DSL provider) still has bad data your cache may also still contain bad records even after rebooting. In that case you'll need to wait for the bad records to time out, which should occur no later than 5/12/16 3:00 PM PDT.
We sincerely apologize for the trouble.