So you just upgraded to Exchange 2013. You send an email and you see that the messages takes a while to deliver. No users are currently on the server however messages are delayed about 20-30 seconds. Typically you would see this if you are sending from Exchange 2013 to any other version of Exchange. I would like to discuss this in a little detail of what you are experiencing.
When you installed exchange 2013. Exchange has the option of choosing which DNS it would prefer to use. If we do not specify this. Exchange will choose which network adapter it would like to use for DNS settings. So if you message track a message using the command Get-TransportServer | Get-MessageTrackingLog –MessageID “MessageIDHere” with a new install of exchange 2013 you will see the following:
As you can see the total latency was 34 seconds. If you look at the MessageInfo line you will the message sat at component code MTSSDMO(MailboxTransportSubmission StoreDriverSubmission SmtpOut) for 32 seconds. For more information on the components that are encountered during message delivery run the following command from the Scripts directory (C:\Program Files\Microsoft\Exchange Server\V15\scripts)
Get-TransportServer | Get-MessageTrackingLog -MessageID "MessageIDHere" | .\ConvertTo-MessageLatency.ps1
What we need to do is specify the DNS server we would like to use for DNS. So basically we are telling exchange look at this DNS server only instead of letting Exchange pick the DNS. To do so Follow the steps below:
Log into ECP
Double Click your Back End Mailbox Server
Choose DNS Lookups
Change “All Network adapters (All available IPv4)” and Specify the network Adapter
Compose a new message and run message tracking. You will see Messages being Delivered a lot faster
If you notice mail delays out of the box with Exchange 2013. Exchange is not broken it is just taking time looking at which DNS adapter it would like to choose. When you look a the DNS Logging you will see we are timing out against AAAA records.
**Note: If you are using NIC teaming you will need to choose the appropriate Teamed NIC. If for troubleshooting purposes you break the NIC teaming and re-create it you will need to Update the DNS server settings to reflect the new Teamed NIC