First off, for more information about what greylisting is, please go to the following URL:
Today we experienced an issue with the greylisting service we have implemented upon our mailservers. Email that was being relayed to our mail forwarding servers was being deferred as the greylisting service was temporarily not accepting new email. As per the configuration for our greylisting, this led to the deferral, and thankfully not an outright rejection, of email, so no emails should have been lost (unless the sending mailserver gave up, which if it does within less than 24 hours, is a misconfiguration on the sending mailserver’s side).
Customers who noticed a lack of email during the day should expect to receive a backlog of email in the near future, if not already.
We apologise for any inconvenience this has caused, and shall be taking steps to ensure this does not happen again.