Autodiscover flow in an Exchange Hybrid environment | Part 1#3 | Part 32#36 5/5 (1)

The Autodiscover flow in an Exchange Hybrid based environment can be considered the most complex flow because the Autodiscover “journey” implemented in two different environments.

Regarding users whom their mailbox migrated to the “cloud” (Exchange Online), the Autodiscover journey will start by the Autodiscover client by addressing the Exchange on-Premises infrastructure.

Article Series Table of content | Click to expand

Exchange and Autodiscover infrastructure | Article Series

Exchange Autodiscover – Article series – INDEX

Exchange and Autodiscover infrastructure | The building blocks

Autodiscover infrastructure | FQDN and URL address

Exchange Autodiscover flow in different environments

Autodiscover infrastructure | Exchange infrastructure and namespace convention

Exchange, Autodiscover and security infrastructure

Autodiscover Troubleshooting tools

Autodiscover major flow scenarios

Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment

Autodiscover flow in an Office 365 based environment

Autodiscover flow in an Exchange Hybrid environment

Exchange Stage migration and Autodiscover infrastructure

Autodiscover flow in an Exchange Hybrid environment | The article series

The first article is the first article in a series of three articles, and the primary focus is -presenting the logic and, the associated components in the Autodiscover flow that implemented in Exchange Hybrid environment.

In the next two articles, we will review the Autodiscover flow that implemented in Exchange Hybrid environment by using the Microsoft web-based tool, the Microsoft Remote Connectivity Analyzer (ExRCA).

Note – you can read more information about how to use the Microsoft Remote Connectivity Analyzer (ExRCA) tool in the article – Microsoft Remote Connectivity Analyzer (ExRCA) | Autodiscover troubleshooting tools | Part 2#4 | Part 22#36

Current article and the next articles

The current article serves as a high-level review of the Autodiscover flow in Exchange Hybrid environment.
The “Autodiscover flow” based on a scenario in which the Exchange on-Premises user mailbox migrated to the “cloud” (Exchange Online).

The user who try to create a new Outlook mail profile be address by default the Exchange on-Premises infrastructure and because the user mailbox is a “cloud” mailbox, the Exchange on-Premises server will send the recipient information about his “cloud E-mail address”.

The Outlook client will start the Autodiscover process by using the “cloud” E-mail address.
In the next articles in this article series, we will “watch closely” the Autodiscover flow by using the ExRCA tool and, analyze each of the different phases that are involved in the process.

The Autodiscover client

The Autodiscover client

The term “Autodiscover client”, describe the element that needs to retrieve the Autodiscover information from the Autodiscover Endpoint (Exchange server).

In the Exchange Hybrid environment, we can point to the type of Autodiscover clients:

1. Exchange mail client

The Autodiscover process that implemented by the Exchange client that needs access to their mailbox.

The Autodiscover client could be any mail client such as- Outlook, mobile device (ActiveSync client) and so on.

2. Server to server

The other type of Autodiscover client could be another Exchange server.

In the Hybrid environment, the Exchange On-Premise infrastructure and the Exchange Online infrastructure operates as one logic entity.

When relating to the subject of Exchange web service, the information is shared between the two different Exchange infrastructures (Exchange on-Premises and Exchange Online (by Relies on the Autodiscover infrastructure.

When Exchange Online infrastructure needs to get information about a particular Exchange on-Premises recipient, Exchange Online will locate the Exchange on-Premises server by using the Autodiscover process.

For example, when a “cloud user” (user who has an Exchange Online mailbox) need to see Free/Busy time of Exchange On-Premise user (user that his mailbox hosted on the Exchange On-Premise server), the request for the information will be sent from the Exchange Online server to the Exchange On-Premise server.

The Exchange Online “find” or “allocate” the Exchange On-Premise server by using the Autodiscover services.

Autodiscover in the Hybrid environment classification 01

Exchange On-Premise and Exchange Online – Best friends forever

The infrastructure of Hybrid environment is very sophisticated and compound and, the Autodiscover infrastructure are only a part of this infrastructure.

In this article, we will relate only to the subject of Autodiscover in Hybrid environment and not to the “other parts” of the Hybrid environment but, it’s imperative to understand that the Autodiscover serves as an infrastructure for many other parts of the Hybrid environment such as – Free/Busy time, Mail tips, out of office, move mailbox (mail migration) and so on.

Exchange on-Premises Server and Exchange Online

Hybrid environment different environment and Exchange client Transparency

The beautiful part in the Hybrid environment is, that although the Hybrid environment is connecting two entirely deferent environment – Exchange On-Premise and Exchange Online environment (and if we want to add more complexity to the description a relationship between the On-Premise Active Directory and the Windows Azure Active Directory) and, despite that fact that the term “Hybrid environment” is composed of many different parts, from the Exchange client’s point of view, this compound infrastructure is “unnoticeable”.

For example, in an Exchange hybrid environment, a recipient named “Alice” wonder if she hosted at the Exchange Online or Exchange On-Premise, for Alice, there is no way to get this information.

My point is that as Exchange administrator in Hybrid environment we have to be familiar with the “inside infrastructure of the Hybrid environment and the Autodiscover process” but, the advantage is that from the user point view, this infrastructure (the Hybrid environment) is transparent.

Hybrid environment different environment and Client Transparency-02

Hybrid environment and SMTP domain name space

Exchange hybrid environment was created for “combing” to different infrastructures into one logical entity.

In Exchange Hybrid environment, the organization user’s mailboxes are “spread” between two different environments – the organization environment (Exchange on-Premises) and the cloud environment (Exchange Online).

The organization users are not aware of this two different infrastructure but in reality, we are dealing with two entirely different environments.

The “magic glow” that sticks together this two different infrastructure implemented by implementing Exchange organization relationships between the two different infrastructures.

Each of the “physical infrastructure” – Exchange on-Premises and Exchange Online needs to relate to the “other” Exchange infrastructure by using a different domain namespace (SMTP domain name space).

  • The Exchange Online environment, relate to objects that physically located at the Exchange on-Premises environment by using the “public domain name.”
  • The Exchange on-Premises environment, relate to objects that physically located at the Exchange Online environment by using the “Hybrid domain namespace.”

Hybrid environment – The different domain namespaces

The ability of Exchange infrastructure to “hide” the complex in from the Exchange client is implemented by “Juggling with the SMTP domain namespaces”.

Exchange hybrid environment – Juggling with the SMTP domain namespaces

The relationships between the recipient E-mail address and the Autodiscover process

In the next section, we will review that subject of the different SMTP domain namespace in the Exchange hybrid environment.

Apparently, there is no clear relationship between the subject of the E-mail address and the Autodiscover process, but in reality, in the Exchange hybrid environment, the Autodiscover flow is fully relying on the user E-mail address.

The connection between the recipient E-mail address and the Autodiscover process

In Exchange hybrid, most of the time the “Autodiscover focal point” is the Exchange on-Premises environment.

As mentioned, organization users don’t really know where their Exchange is mailbox is located.

In a scenario in which user mailbox located at the Exchange Online infrastructure, the organization user will start the Autodiscover journey by addressing the Exchange on-Premises infrastructure and the Exchange on-Premises will notify him, that he needs to restart the Autodiscover journey by addressing different Exchange infrastructure – the Exchange Online infrastructure.

Hybrid environment – the Autodiscover redirection process

The SMTP domain namespaces in an Exchange hybrid environment

In Exchange Hybrid, there is a minimum of a three domain name space. The Exchange hybrid environment is using two domain namespaces and the third domain namespace “belong” to the Office 365 infrastructure.

Hybrid environment – multiple domain names -01

1. Public domain name (public SMTP domain name)

This public domain name is the “formal” organization domain name that is used by the Exchange On-Premise infrastructure and in a scenario of Hybrid environment, the public domain name is also used, for “representing” cloud recipient.

Exchange on-Premises recipient and the Exchange Online recipient will continue to use an E-mail address that uses the “public domain name”.

For example, in a scenario in which the public domain name is o365info.com all the organization recipients whom their mailbox located at Exchange on-Premises and the organization user whom their mailbox located on Exchange Online will continue to use the particular domain name.

This public domain name described as – “shared domain name” because it shared between two different Exchange Online infrastructures (Exchange on-Premises versus the Exchange Online infrastructure).

2. Office 365 Tenant built-in domain namespaces

When we open a new Office 365 subscription, we are required to provide an “organization name.”

In our scenario, the Office 365 tenant domain name is – 365info2

After we provide the required organization name, Office 365 start an automatic process in which it creates two new “Office 365 tenant domain names”.
Based on the Office 365 tenant domain name, the following two domain names are created.

  1. onmicrosoft.com
  2. mail.onmicrosoft.com

Onmicorosft domain name | The default tenant domain name

The second domain name could be described as the “default Office 365 tenant domain name”. This domain namespace is not used by the Exchange hybrid environment.

In case that the organization name who was registered at Office 365 is – 365info2, this name will be “attached” to the office 365 default domain name – onmicrosoft.com and, the result is a domain name that represents the specific Office 365 tenant. In our scenario – 365info2.onmicrosoft.com

Hybrid environment – multiple domain names -02

The 365info2.onmicrosoft.com domain namespace is used only by the Office 365 and Exchange Online environment.

Q: What is the reason for this “default Office 365 domain name”?

A: There are two main reasons:

The need for using a “dedicated domain namespace” such as 365info2.onmicrosoft.com was created for two main reasons –

Reason 1 – Each “entity” in Office 365 must have a UPN name which includes a domain name suffix, and each of the Exchange Online entities (such as recipient) must have an E-mail address that includes a domain name suffix.

When we create the Office 365 tenant, the Exchange Hybrid still does not exist or is not yet defined, and the Office 365 infrastructure needs some kind of “identity” for the Office 365 objects such as users.

Chronologically, Office 365 “doesn’t know if we are going to build and implement an Exchange Hybrid environment.

Reason 2 – Office 365 infrastructure can “host” a local object (users, mailboxes, etc.) that doesn’t relate in any way to the Exchange Hybrid infrastructure.

In case that we create such object, for example, a “cloud user” that not synchronized from the On-Premise Active Directory, this object needs to have an identity.

Onmicorosft domain name | “Hybrid domain namespace”

The third “Office 365 domain name” that is created by default could described as the “Exchange Hybrid domain namespace”.

This particular domain namespace will be used only in Exchange hybrid scenarios.

The structure of the “Hybrid domain namespace” is based on the following formula –
<Office 365 organization name> + <mail> + < onmicrosoft.com>

In case that the organization name that was registered at Office 365 is – 365info2, this name will be “attached” to the “mail” domain name + the office 365 default domain name – onmicrosoft.com and, the result is the Exchange hybrid domain name – 365info2.mail.onmicrosoft.com

Hybrid environment – multiple domain names -03

The Exchange Hybrid domain namespace used by Exchange on-Premises infrastructure for routing purposes.

The “routing” is related to two different infrastructures

1. Mail flow

Each time that Exchange On-Premise server recipient needs to send an E-mail message to the Exchange Online recipient, the request will be accepted by the Exchange on-Premises that “understand” that the destination recipient located at the Exchange Online infrastructure.

The Exchange on-Premises will use the “Hybrid domain namespace” of the destination recipient. In Exchange Hybrid, the each of the mail message that sent to the Exchange “Hybrid domain namespace” will be routed to the Exchange Online server.

2. Autodiscover flow

The use of “Hybrid domain namespace” is also related to the Autodiscover flow in an Exchange Hybrid environment.

When a user whom his mailbox located at the Exchange Online infrastructure, try to get Autodiscover information, he will address the Exchange on-Premises server.

When the Exchange on-Premises server “notice” that the recipient considers as an Exchange Online recipient, the Exchange on-Premises send as a reply the E-mail address that includes the “Hybrid domain namespace.” In our scenario – 365info2.mail.onmicrosoft.com

When the Autodiscover client gets this information, he “understands” that he needs to create a new Autodiscover process, but now, address the Autodiscover Endpoint that is responsible for the domain name – 365info2.mail.onmicrosoft.com

In the following diagram, we can see the logic structure of the SMTP domain name in Hybrid environment.

Hybrid environment – multiple domain names -04

Hybrid environment | recipients and their E-mail address

To demonstrate to the concept of multiple E-mail addresses in the Hybrid environment, let’s use the following scenario:

Alice is a corporate employee whom her mailbox was “relocated” (moved) to the cloud (Exchange Online).

In the Exchange On-Premise server, Alice is configured as a Remote mailbox.
The Exchange On-Premise “know” that Alice has two E-mail address: the standard public E-mail address – Alice@o365info.com and additionally, the “Hybrid environment service domain E-mail address – Alice@o365info2.mail.onmicrosoft.com

In Office 365 and Exchange Online, Alice will have the same two E-mail addresses and additional E-mail address – Alice@o365info2.onmicrosoft.com

The “additional E-mail address”, the E-mail address (the E-mail address without the “subdomain: mail) is based on the “Office 365 SMTP domain name” that automatically allocated to each of Office 365 users who have a mailbox.

Hybrid environment - Recipients their additional Alias E-mail address 02

To demonstrate the difference between the Exchange On-Premise environment and the Exchange Online environment, let’s take a look at Alice’s mailbox proprieties.

In the following screenshot, we can see Alice’s mailbox proprieties in Exchange On-Premise.

As we can see, Exchange On-Premise “know” about two E-mail address that Alice has.

The E-mail address – Alice@o365info2.mail.onmicrosoft.com is based on the SMTP domain name that we call “service domain name” in Hybrid environment.

Exchange on-Premises refers to the “Exchange Online E-mail address” as –
Routing E-mail address.

Routing E-mail Address in Hybrid environment

Exchange 2013 server interface

Exchange hybrid   - Routing E-mail address -external E-mail address- Exchange -2013

In the next screenshot, we can see Alice’s mailbox proprieties in Exchange Online.
As we can see, the Exchange Online “know” about three E-mail address that Alice has.
The “additional E-mail address” that Alice has is – Alice@o365info2.onmicrosoft.com

Alice E-mail address on Exchange Online

Why are you telling me all of this information?

In case that you’re wondering – “how does this information relate to me”?

The answer is that we need to understand the Hybrid environment infrastructure such as the subject of the E-mail address and the multiple SMTP domain name spaces, so we will be able to comprehend better the Autodiscover workflow in a Hybrid environment.

The need to understand the Hybrid infrastructure

Hybrid environment | Exchange on-Premises recipient versus Exchange Online recipient the Autodiscover flow

In Hybrid environment, the user organization user’s mailbox can be hosted on the Exchange on-Premises infrastructure or the Exchange Online infrastructure.

The main difference between the Autodiscover flow for Exchange on-Premises recipient versus, Exchange Online recipient is that for Exchange on-Premises recipient, the Autodiscover Endpoint is the Exchange on-Premises server.

Regarding recipients that their mailbox hosted at Exchange Online, the Exchange
on-Premises serve just as an element that will serve for routing Autodiscover client request to the Office 365 Autodiscover infrastructure.

For recipients whom their mailbox located at the Exchange on-Premises, the Autodiscover flow is implemented in the following way:

  1. The Autodiscover will access the local On-Premise Active Directory (using an LDAP query), asking for a list of Exchange On-Premise server\s that can provide him the required Autodiscover information.
  2. The Autodiscover client will connect local DNS server, asking to resolve the host’s name\s of the local Exchange On-Premise server\s that was returned by the On-Premise Active Directory.
  3. The Autodiscover client will try to connect the Exchange On-Premise server
    Hybrid environment  - Autodiscover in On-Premises Active Directory environment - Exchange On-Premise mailbox-01

Regarding the Autodiscover flow in an Exchange hybrid environment, for recipients whom their mailbox hosted at Exchange Online, the Autodiscover flow is a little be more complicated and involved additional steps.

For recipients whom their mailbox located at the Exchange Online, the Autodiscover flow is implemented in the following way:

  1. The Autodiscover will access the local On-Premise Active Directory (using an LDAP query), asking for a list of Exchange On-Premise server\s that can provide him the required Autodiscover information.
  2. The Autodiscover client will connect local DNS server, asking to resolve the host’s name\s of the local Exchange On-Premise server\s that was returned by the On-Premise Active Directory.
  3. The Autodiscover client will try to connect the Exchange On-Premise server.
  4. The Exchange On-Premise response with a “redirection message” informing the recipient that for getting the required Autodiscover services, he will need to use a different E-mail address, his Office 365 tenant E-mail.
  5. Exchange client will start the Autodiscover process all over but now, by addressing the Exchange Online infrastructure.
    Hybrid environment - Autodiscover in On-Premises Active Directory environment  - Remote Mailbox -02

To demonstrate the process of Autodiscover flow in the Hybrid environment, for a recipient that his mailbox is hosted in the cloud (Exchange Online), Let’s use the following scenario:

  • Alice’s mailbox is hosted at Exchange Online (the Exchange infrastructure is based on Hybrid environment).
  • Alice needs to create a new Outlook mail profile, so she will be able to connect to her mailbox (Exchange Online mailbox).
  • The Exchange on-Premises relate to Alice’s mailbox as a “remote mailbox”.

Step 1 – Locating Autodiscover Endpoint in Active Directory-based environment.

I in a scenario of the remote mailbox (cloud mailbox) the first part of the Autodiscover flow is identical to the Autodiscover flow that implemented by a recipient who has a “standard mailbox” on the Exchange On-Premise server.

When Alice tries to create a new Outlook mail profile, Outlook will query the local On-Premise Active Directory for the name\s of Exchange On-Premise servers which provide the required Autodiscover services.

Outlook will locate an optional Exchange On-Premise server and ask him for the required Autodiscover information.

Autodiscover flow in Hybrid environment - Exchange Online mailbox - Phase 1 of 4

Step 2 – Addressing the Exchange on-Premises server

Technically speaking, Exchange server doesn’t know who “Alice” is. To be able to get detailed information about Alice, Exchange on-Premises contacts the local On-Premise Active Directory asking for information about Alice.

The answer from the On-Premise Active Directory, include information about the fact that Alice’s mailbox is a “Remote mailbox” and Alice has the following Routing E-mail Address –
Alice@o365info2.onmicrosoft.com

Autodiscover flow in Hybrid environment - Exchange Online mailbox - Phase 2 of 4

Step 3 – Autodiscover client starts the Autodiscover flow by addressing Exchange Online infrastructure.

The Autodiscover client will start a new DNS query looking for a host named – o365info2.onmicrosoft.com

Note – in most of the scenarios, this name will not be resolved but instead, only the hostname – Autodiscover.o365info2.onmicrosoft.com

Autodiscover flow in Hybrid environment - Exchange Online mailbox - Phase 3 of 4

Step 4 – verifying if the Autodiscover Endpoint can communicate using HTTPS.

The Autodiscover client will try to create an HTTPS session to the “destination Autodiscover Endpoint” (Exchange Online) asking for the required Autodiscover services.

Autodiscover flow in Hybrid environment - Exchange Online mailbox - Phase 4 of 4

The next articles in the current three articles series are:

In this articles, we will use the ExRCA tool for providing a detailed review the Autodiscover flow in Hybrid environment

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Autodiscover flow in an Exchange Hybrid environment | Part 1#3 | Part 32#36
Description
The Autodiscover flow in an Exchange Hybrid based environment can be considered the most complex flow because the Autodiscover “journey” implemented in two different environments.Regarding users whom their mailbox migrated to the “cloud” (Exchange Online), the Autodiscover journey will start by the Autodiscover client by addressing the Exchange on-Premises infrastructure.
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