Exchange 2016 - Outlook inside company network CANT connect without Internet connection.

Question

Exchange 2016 - Outlook inside company network CANT connect without Internet connection.

Gudakesh Sharma 26

Outlook inside company network (Intranet) can not load or connect to exchange 2016 automatically without aan internet connection. Both my lab exchange 2016 server and lab PC with outlook 2013 are on same network but without Internet it does not connect to exchange. When i turn Internet ON then it works. AutodiscoverServiceInternalURI for my CAS service is - https://autodiscover.domain.com/autodiscover/autodiscover.xml. I have also checked with https://serverfqdn/autodiscover/autodiscover.xml AutodiscoverServiceInternalURI is responsible for connecting within Intranet, correct ? What am i missing here ?

Andy David - MVP 157.9K Reputation points MVP Volunteer Moderator

2021-03-11T17:54:42.177+00:00

What is set for the MAPI HTTPS virtual directory URLs ( I assume you are using MAPI HTTPS)

https://learn.microsoft.com/en-us/exchange/clients/mapi-over-http/configure-mapi-over-http?view=exchserver-2019
Gudakesh Sharma 26 Reputation points

2021-03-14T09:08:16.333+00:00

Since its an Exchange 2016, MapiHttp is enabled at org level and mailbox level as well.
MapiHttps virtual directory Internally is set to : https://serverfqdn/mapi And External is $null

Authentication is On for all (NTLM, Basic, Windows Kerb, OAuth, Negotiate)

Test-outlookconnectivity command also results positive but still outlook can not make connection without internet.
Gudakesh Sharma 26 Reputation points

2021-03-14T11:03:25.153+00:00

For Outlook 2013 --
When I remove the default gateway and change the default gateway to be my DNS\DC server on the PC, outlook works internally without internet as well.

After that when I remove the default gateway completely from the PC and leave it blank , outlook can connect to the exchange server internally as well.

Just need to understand whats happening here ? why does it started working internally when i used my DC\DNS as the gateway and then removed it as well , and it does not work with the default gateway which is what i have for internet?

For Outlook 2010 --
When I remove the default gateway and change the default gateway to be my DNS\DC server on the PC, outlook works internally without internet as well. Outlook 2010 does not work with NO default gateway on the PC
KAI SENG 30 Reputation points

2023-06-20T07:44:26.4966667+00:00

This is super weird. I do exactly what you mentioned. Set the default gateway to DNS/DC server and all of a sudden, outlook works internally in my testing environment without Internet.

Someone from MS should look into this.

1 answer

Your answer

Andy David - MVP 157.9K Reputation points MVP Volunteer Moderator

2021-03-11T17:54:42.177+00:00

What is set for the MAPI HTTPS virtual directory URLs ( I assume you are using MAPI HTTPS)

https://learn.microsoft.com/en-us/exchange/clients/mapi-over-http/configure-mapi-over-http?view=exchserver-2019
Gudakesh Sharma 26 Reputation points

2021-03-14T09:08:16.333+00:00

Since its an Exchange 2016, MapiHttp is enabled at org level and mailbox level as well.
MapiHttps virtual directory Internally is set to : https://serverfqdn/mapi And External is $null

Authentication is On for all (NTLM, Basic, Windows Kerb, OAuth, Negotiate)

Test-outlookconnectivity command also results positive but still outlook can not make connection without internet.
Gudakesh Sharma 26 Reputation points

2021-03-14T11:03:25.153+00:00

For Outlook 2013 --
When I remove the default gateway and change the default gateway to be my DNS\DC server on the PC, outlook works internally without internet as well.

After that when I remove the default gateway completely from the PC and leave it blank , outlook can connect to the exchange server internally as well.

Just need to understand whats happening here ? why does it started working internally when i used my DC\DNS as the gateway and then removed it as well , and it does not work with the default gateway which is what i have for internet?

For Outlook 2010 --
When I remove the default gateway and change the default gateway to be my DNS\DC server on the PC, outlook works internally without internet as well. Outlook 2010 does not work with NO default gateway on the PC
KAI SENG 30 Reputation points

2023-06-20T07:44:26.4966667+00:00

This is super weird. I do exactly what you mentioned. Set the default gateway to DNS/DC server and all of a sudden, outlook works internally in my testing environment without Internet.

Someone from MS should look into this.

Answer 1

Eric Yin-MSFT 4,396

Hi,
Which URL is set for AutodiscoverServiceInternalURI actually?
When you turn Internet OFF, pressing CTRL and right-click Outlook icon, select Test Email Autoconfiguration, typing the account and password, a normal test looks like:

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Gudakesh Sharma 26 Reputation points

2021-03-14T09:10:12.74+00:00

AutodiscoverServiceInternalUri is - https://webmail.company.com/autodiscover/autodiscover.xml

Given that I have multiple 2016 Servers in my Lab, if autodiscover fails to this url then it should ideally connect to another server from SCP list since I am only trying to connect internally without internet connection.

Kindly suggest
Eric Yin-MSFT 4,396 Reputation points

2021-03-19T09:44:12.417+00:00

There's not any SCP list:
A Service-Connection-Point (SCP) object is created in Active Directory. The object contains a URL to the AutoDiscover service. This is for intranet clients so they do not have to use DNS to locate the AutoDiscover service.
Use adsi.edit to check:
DC=<domain>, CN=Configuration, CN=Services, CN=Microsoft Exchange, CN=First Organization, CN=Administrative Groups, CN=Exchange Administrative Group, CN=Servers, CN=<CAS Name>, CN=Protocols, CN=AutoDiscover, CN=<CAS Name>
Have a test in EXRCA with your Internet closed: https://testconnectivity.microsoft.com/tests/Ola/input

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Exchange 2016 - Outlook inside company network CANT connect without Internet connection.

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