Outlook and default gateway

Question

Hello,

There's the post regarding the default gw issue with Outlook here but that post doesn't explain the reason for that strange behaviour: Outlook won't connect to Exchange with non-existing machine's default gateway.

Example 1: Creating a new profile in Outlook 2019 on a machine with no configured default GW:

By the way - among MS's suggested reasons for the error above there's no "missing default gw" reason.

Example 2:

2a) default gw is configured but that host does NOT exist = no connection to Exchange:

2b) correct gw settings = connection can be established (although external DNS lookups still do not work!)

2c) default gw is configured but the host specified as the GW is NOT the gateway (it's the DC in this case) - Outlook still connects without issues:

The answer to the post in the begining of this post is
"To allow Outlook client to access Exchange server while client is no Default Gateway configured, we need add a registry to set DefConnectOpts to "0"" but I'd like to know

Q) What's the purpose of having Outlook to check the availability of a default gateway if a client can already "see" a server?

The problem is much broader then just "while client is(has - my correction) no Default Gateway configured" - as you've seen above a client could have his/her gw configured properly but Outlook would refuse the connection should a gw go off-line for some reason. In fact it means ANY Outlook client should have this registry fix applied to avoid this kind of problem...

Answer 1

Hi @Mikhail Firsov

I have seen this issue before and the symptoms are the same.

There was actually a Microsoft KB on this issue but it is no longer available.
You may check it via archive sites.
Here is a link:
Error messages when you try to connect Outlook 2007 to Exchange Server: "The action cannot be completed" or "Your Microsoft Exchange Server is unavailable" or "Cannot start Microsoft Office Outlook"
(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

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