Exchange Online - Autodiscover XML response not returning Outlook settings

[Divvy]

Hi everyone,

We are currently involved in a support case for one of our users that is unable to access her e-mail account when using Outlook desktop version, webmail is working as expected. The mailbox is located in Exchange Online, but the AD account is synced from local AD with a Hybrid Configuration for Exchange 2016.

The DNS autodiscover.domain.com for the affected user is pointing to the OnPremises Exchange URI since we still have some mailboxes that have not been migrated, but since we use M365 apps Outlook it should try to contact Exchange Online autodiscover first anyway.

Usually when we run into this, it is because the user is not licensed for M365 apps or does not have the requried Exchange Online license, but this user has both Exchange Online Plan 2 and M365 Enterprise Apps. The licensing is done using group based licensing in Azure AD. We have also checked that MAPI (everything except smtp auth) is enabled on her account in the M365 admin portal.

If i run the Outlook Connectivity test in the testconnectivity microsoft site, we only get a <Type>Web</Type> response in the XML. (usually you get EXCH, EXPR, EXHTTP etc)

My understanding is that this indicates an classification/license problem in Exchange Online for the user, but the support case has been transfered to the "Outlook desktop app" team which are insisting that we must collect Outlook logs to troubleshoot further since OWA is working.

The case is already over a month old, and i dont feel like starting from scratch again. I would love a second opinion on my interpretation that this is a Exchange Online issue, and not related to Outlook desktop app before i attempt to escalate the case.

[#2]

Is there a User account in on-premises AD for this user and is it configured correctly? You should be able to see the user in the on-premises Exchange Admin as an Office365 user. If not that indicates the on-prem account is not configured correctly and thus not redirecting the Autodiscover to EXO

[#3]

@Dan Snape Yes, we do have an onprem user object and remote mailbox, which are configured correctly. When using M365 Enterprise Apps, Outlook should also automatically first try the M365 autodiscover service before attempting to resolve DNS. I think this is hardcoded in the application.

Just to be sure i tested the OnPrem Autodiscover for the user, and it returns:
<RedirectAddr>username @ tenant.mail.onmicrosoft.com</RedirectAddr>

[#4]

Have you confirmed everything is ok with the mailbox by using OWA? Outlook has registry settings that control whether it points to EXO or uses DNS (plus some other options) so it's worth checking them as well. Testing Outlook autoconfiguration will also show you where it's going wrong

[#5]

This is because it is set to search for autodiscover-related servers in the Internet environment first.
[Action Item]
Add the key value to the following registry path and reboot to check the symptoms!
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\15.0\Outlook\AutoDiscover]
“ExcludeHttpsRootDomain”=dword:00000001

[#6]

We dont really have any issues with the autodiscover query process itself, its just that the content in the XML that is returned by Exchange Online does not appear to contain the required information.

If you run the Outlook Connectivity test on your own M365 mailbox, and expand the autodiscover XML result, you will see that values for different connection types are returned depending on your license level. (WEB, EXCH, EXPR, EXHTTP)

For the affected mailbox the only connection type returned is WEB, which i think is wrong when it is licensed for use with desktop applications.

[#7]

you'll probably need to involve Microsoft via a support ticket if the incorrect autodiscover results are being returned from Exchange Online