Slow mail delivery on Exchange 2013

I had noticed on a couple of Exchange 2013 deployments that mail delivery was slower than expected.  With previous versions of exchange internal emails were delivered almost immediately.  However on the Exchange 2013 servers I was noticing that internal emails were taking up to 5 seconds to be delivered.  That may not sound like long but people were starting to notice the delay.   I installed service pack 1 and the latest cumulative update but the issue persisted.  I dug a bit deeper into the issue and discovered that it was being caused by the DNS lookup settings.  The default setting was set to “All Network Adapters”.  Configuring the specific network adapter resolved the issue straight away.  Interestingly the servers only had one network adapter.

To access the required setting

Click on Servers in the main menu

EAC Menu - Step 1

Edit your server

Click on DNS Lookup in the menu then change both adapters from All Network Adapters to your specific network adapter.

EAC - Step 3

Your mail should now be delivered instantly.

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