One of our email service partners, Rackspace, has announced emergency maintenance to their email service.
Outgoing mail is unaffected, but there will be problems attempting to check/receive mail. Please check their status page here for more information, and contact us for any further assistance or information.
See comments below for further updates.
Full detail of this disruption can be viewed here.
Latest update 20 mins ago:
Rackspace report that delivery times have now returned to normal.
Occasionaly errors may persist checking mail due to increased load while the backlog is cleared.
Rackspace have been working through the weekend to restore normal email service, and have provided the following detail summarising the causes and resolution of the disruption: