We're in the process of moving some services to our new datacentre in Amsterdam. I've just pointed our secondary MX and nameserver there, which means that the IP addresses of ns2.messagingengine.com and in2-smtp.messagingengine.com have changed.

The new addresses will propagate over the next 24 hours, after which time the old servers in Iceland will be shut down.

Unless you've hard-coded the old addresses somewhere, you shouldn't see any difference.