This weekend we updated our DNS to a different ISP. We made the change Friday night around 6 pm and it updated Saturday night around 6 pm. Emails are coming through when it is slow, but during the peak hours it slows down. Even internal emails are taking 1-2 hours to arrive. I do not know what to look for to see what is causing the problems. There are about 4000 emails in the Queue Viewer on the Exchange Management Console.
Just for your information... we use a fatpipe system to bond three different ISP lines. Traffic is aggregated depending on which line has the best latency.
When we were making the change we removed the DNS forwarders on the exchange server that went to our old line, and added the DNS info for the new line. It seems to me that we would need all 3 DNS information on the exchange server, does that seem right?
Does anyone know what I should try to determine what is causing the queuing? Any help is greatly appreciated.