Outlook Anywhere difference between ExternalHostname and InternalHostname parameter

adam900331 366 Reputation points
2021-03-30T10:04:33.85+00:00

Hy!

The Outlook Anywhere (RPC over HTTP) lets client connect with their Outlook to Exchange from outside of the LAN for example over the internet. When I set up the OA there are two URL what I can configure, ExternalHostname and InternalHostname. I think the clients will be use the ExternalHostname URL parameter when they are on the internet. And when clients use the InternalHostname URL? When the clients connect to the Exchange in LAN? I tested it, and remove the parameter from the InternalHostname URL, and the client still can connect to the exchange in LAN.

Thanks.

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 152.3K Reputation points MVP
    2021-03-30T12:22:38.833+00:00

    Not having those URLS defined doesnt mean clients cant connect, its just the name autodiscover passes to the client.
    Internally, domain-joined clients will be able to connect to Exchange.
    If you remove that internalHostName and than do an Test Email AutoConfiguration: https://kb.intermedia.net/article/2150, you can see what is returned by Autodiscover

    External Clients connect to the ExternalHostName, but if the internalhostname is resolvable externally, they can still connect as well.

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