Outlook takes 40 seconds stuck at "trying to connect"

Anonymous
2021-10-22T21:55:45.267+00:00

Riddle me this batman. I have an isolated lab environment which doesn't have internet access, but does have Exchange, Domain Controllers, and client machines running Outlook. When opening Outlook in this isolated environment, it takes about 40 seconds for Outlook to find and connect to Exchange. If I jump into the lab firewall and give said client internet access, this problem goes away. Outlook client connects to isolated Exchange server instantly.

Exchange 2016 on-prem and Windows 10. Outlook version 2013.

Regards,
Adam Tyler

Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Andy David - MVP 139.8K Reputation points MVP
    2021-10-22T22:09:19.103+00:00

    Fire up fiddler on the workstation and see what the client is trying to connect to


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  1. Anonymous
    2021-10-22T22:46:18.393+00:00

    Sure enough. Once I whitelisted the IP that this resolves to, Outlook fires right up in dev with all other traffic blocked. Unfortunately the list of IPs associated with this FQDN seem to rotate depending on what public DNS server you query. So something you'd have to look every time.

    Regards,
    Adam Tyler

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