We are aware of SMTP flood attack on our main mail gateways. This is causing legitimate email to be delayed slightly. 

Since this appears to be an IP based attack, and repreat DNS lookup's are not being performed within the TTL of the record, we have temporarily diverted traffic to another address in the block to minimise the impact of this attack. 

We are of course blacklisting IP subnets as we can to reduce the impact, but this is a botnet attack coming from thousands of IP's so keeping ahead of it is a slow process. 

Customers experiencing a delay in receiving email can be assured that email will be delivered but with a short delay. 

12:00 - This seems to have subsided. We will continue to monitor but there should be no delay in email delivery now.