We are experiencing delays in the delivery of domain filtered emails for one of our servers at the moment. This doesn’t affect all emails and only emails sent to domain filtered address, not POP3/IMAP filtered ones.
We are currently working on setting up new servers and fixing the faulty one and expect it to be solved later today. We regret the inconvenience.

Update: We have now solved this and moved traffic to new servers, replacing the faulty one. There should no more delays and all delayed messages should now have been delivered.