Executive summary: Outlook 2016 users may find themselves disconnected when Autodiscover is not present for your unit’s domain name.
Over the last few months we have noticed a rise in the number of Outlook connectivity incidents reported to the helpdesk. In many cases we are finding that the issue is linked to a combination of two things: the use of Outlook 2016 and the absence of a resolvable autodiscover entry for that individual’s domain name. We know that some units have delayed getting those records created, relying on the fact that you could still get basic Outlook-Exchange connectivity via legacy (unsupported) Exchange 2003 RPC over HTTP. This method no longer works in Outlook 2016 because this version has dropped support for Exchange Server 2003.
This has not been a significant support issue until now. It was around the time that email was being migrated from Herald into Nexus that we first sent a message to IT Support Staff requesting the creation of autodiscover DNS entries. At that time we were suggesting it to primarily help brave souls with Outlook 2007. Today that advice still stands, but in order to support current, and future, versions of Outlook these DNS records have now become a necessity, not a ‘nice to have’.
The University strongly recommends that each unit/college/department who manage their own DNS should create an autodiscover entry. This is the recommended solution for both on on-premises Exchange and when mailboxes are in the Office 365 cloud. It therefore takes care of Nexus now and into the future. You should ensure that your DNS includes an autodiscover CNAME or A record for your domain name (such as autodiscover.it.ox.ac.uk) which can be used to resolve all related email addresses. These should point to autodiscoverredirect.nexus.ox.ac.uk.
Once all of that is done:
To improve performance for Outlook 2016 you may also wish to use the following Registry settings which will force Outlook to bypass root domain discovery and redirect to the autodiscover CNAME or A record to resolve the address. This saves a little lookup time by bypassing initial root domain queries.
In the key HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover create/modify a DWORD value of ‘ExcludeHttpsRootDomain’ with a value of ‘00000001’.
Group Policy can do this too via ‘Exclude the root domain query based on your primary SMTP address’ setting.