We're currently experiencing issues on parts of our Mail Platform. This affects a part of our users, that cannot send or receive mail at this moment. Also, the webmail-client is unavailable for these customers. Our technicians are investigating the problem and we're working very hard to resolve the issues as quickly as possible. We will add more information once it becomes available. Our sincere apologies for the inconvenience.
The cause of the issue was determined to be a corruption on one of the disks in our mail cluster. The disk has been been repaired, solving the issues.