Update 06/04 @ 09:00: The issue is now resolved.  All backlogged mail should be delivered in the near future.

Update 06/04 @ 08:17: We are continuing to work with our supplier to get this fixed.  Next update expected at 09:00.

We are aware of an issue affecting inbound and outbound email which began at ~12:15 yesterday lunchtime (04/04).  This is ongoing and has been raised with our provider.

An update will be posted in due course once we have more information.