This morning at approximately 09:30GMT a number of domains hosted by us came under a “joe-job” style attack This lasted untilapproximately 12:00GMT. This is where a large number of emails are sent with the sender forged to appear as a domain hosted by us. As a result many mail servers reject the mail and the bounce message is returned to us, even though it was not sent by us.
This lead to a surge in the amount of mail our incoming mail servers had to handle. As a result some mail delivery was delayed during this period as the mail is processed in a queue on a “first come first processed” basis. During this process one of the mail servers froze and needed to be restarted a number of times.

The result of this restart means that it is possible some users will have received the same email multiple times. This can happen if the restart is performed at the exact same time as the message is being processed. Since the mail server does not know if the mail was delivered successfully upon restart to be safe it delivers the message again. As the SMTP service on this particular server had to be retarted 6 times in the space of five minutes it is possible some customers may even have received the same email 5 or 6 times.

We have identified the reason for the SMTP server freezing. It was a badly written rule which required more processing than necessary. This rule has now been streamlined and the processing returned to normal.

All mail queues have now returned to normal and processing mail in a timely manor.

We apologise for any inconvenience this may have caused.