Quoted from Plus.Net: 

This major incident occurred as a result of human error during work to resolve timeouts when collecting mails, which we reported via service status last week: http://usertools.plus.net/status/archive/1152295291.htm

As of Sunday morning, things had progressed well, and we were on track to solve the issues with mail timeouts, which had started to occur following our move to a new email storage system.

At 8AM on Sunday morning our engineers were in a position to switch over to use of the new storage solution. As the first stage of this, an engineer was in the process of bringing the new back-up storage More >