How Autodiscover works in Exchange Online, Exchange On-Premise and Hybrid Exchange – Part 3

December 24th, 2018 | Posted by admin in Exchange

On the last part, we saw how the auto discover works for customers in Office 365 alone. In this post we will see how the Autodiscover working on Exchange On-Premise and Hybrid Edge environment.

How Autodiscover works in Exchange On-Premise?

If a company has their messaging infrastructure in On-Premise alone, this is how the Autodiscover works for Exchange Online Mailbox

  1. Once the user launches the outlook and enter the credential, Outlook will query AD for SCP record to get the Autodiscover Service information.
  2. Once the information available, it will validate the user and try to connect the url which will go to the client access server
  3. CAS server query AD and send the Autodiscover and other exchange related services information in XML file
  4. Outlook uses that information to configure outlook profile.

Below the Test E-Mail Autoconfiguration result that explains the above behaviour

How Autodiscover works in Exchange Hybrid Environment?

Hybrid Exchange environment is nothing but a customer having few mailboxes in On-Premise Exchange and few in Office 365 (Exchange Online). Though both the exchange infrastructure are different, Hybrid Configuration Wizard make those 2 environments coupled together and function as a single environment.

Below the details on how Autodiscover works for a user mailbox in Office 365 for Hybrid environment user.

In above illustration, company user dhanya.com as their SMTP address space and for the mailboxes in Office 365, On-Premise will have a remote mailbox account with the target address as dhanyaonline.mail.onmicrosoft.com as the target address.

  1. Once the user launches the outlook and enter the credential, Outlook will query AD for SCP record to get the Autodiscover Service information.
  2. Once the information available, it will try to validate the user and it can’t find mailbox for Raj and only remote mailbox account available for this user in On-Premise and it will inform outlook to try Autodiscover request for Raj’s Target Address.
  3. Outlook will try to get the Autodiscover information for dhanyaonline.mail.onmicrosoft.com by dns query to internet. Autodiscover.dhanyaonline.mail.onmicrosoft.com will have a CNAME record that points to Exchange Online Autodiscover record
  4. Outlook will connect Autodiscover.outlook.com which will connect to Exchange Online client Access server
  5. Exchange Online validate the user by an authentication prompt
  6. Once verified, Exchange Online will send the Autodiscover information in xml formal to user.

Below the Test E-Mail Autoconfiguration result that explains the above behaviour which clearly shows the above explanation

We see lot of information on how the Autodiscover works for Exchange Online, Exchange On-Premise and Hybrid Exchange environment with explanations. I hope this is informative to you. Leave your comments if any additional information required.

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