Spam scanning issue with third party vendor

The issue is resolved.

The problem was caused by a third party scanning engine which provides us with insight into zero day threats across the globe in near real time. Due to a fault with their classification system, UK emails were falsely classified for a period of 55 minutes. The results of this engine are used as part of our overall determination of whether an email is considered spam and because those results are cached by our systems, we continued to falsely classify legitimate emails even after the vendor fixed their issue.

We mitigated the effect by temporarily reducing the weighting assigned to this engine.

Going forward we will be creating a system which will allow us to respond more quickly to the need to clear caches. This will be included as a future system upgrade.

Please accept our apologies for the disruption this caused.

We are still monitoring the status of the update we made this morning, but we think that it has stopped the False Positives. We’re currently working with the vendor to identify the root cause.

Some calendar invites were also being blocked and we think this should be resolved now.

We are currently resolving an issue reported today by multiple customers that is causing emails to be flagged as spam more aggressively by third-party scanning engine Cyren.

We have temporarily adjusted the weight used for this engine and we are continuing to look into available steps to remedy the situation.

Detection should have returned to a more normal level with the adjusted weight but we will continue to monitor the situation.