Autodiscover flow in an exchange on premises environment non-active directory environment part 2#3 part 27#36
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This document provides a detailed overview of the autodiscover process in a non-active directory environment, focusing on various scenarios that an autodiscover client may encounter. It outlines the methods and steps that the client takes to locate the autodiscover endpoint, including scenarios with HTTPS support, HTTP redirection, and the use of SRV records. The emphasis is on understanding the autodiscover flow and the challenges faced in different configurations, particularly for clients creating new Outlook profiles.
Autodiscover flow in an exchange on premises environment non-active directory environment part 2#3 part 27#36
- 1. Page 1 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Autodiscover flow in an Exchange on- Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 The current article and the next article, will be dedicated for detailed review of the Autodiscover flow, that is implemented in an Autodiscover flow in an Exchange on- Premises environment | non-Active Directory environment, by using the Microsoft web-based tool, the Microsoft Remote Connectivity Analyzer (ExRCA). Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment | The article series The current article is the second article in a series of three articles. The additional articles in the series are:
- 2. Page 2 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 1#3 | Part 26#36 Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 3#3 | Part 28#36 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 The essence of the Autodiscover journey The main purpose of the “Autodiscover journey” that is implemented by the Autodiscover client is to find his Autodiscover Endpoint.
- 3. Page 3 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Technically speaking, there are many types of scenario in which the Autodiscover client will initialize the Autodiscover process and different type of Autodiscover clients. For this reason, we will need to focus on specific examples of the variety of possible scenarios. To demonstrate the process of Autodiscover in a non-Active Directory environment, we will review the scenario of a client that needs to create a new Outlook mail profile, in an environment that described as non-Active Directory environment.
- 4. Page 4 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 In the following diagram, we can see the flow of the Autodiscover algorithm which the Autodiscover client is “programmed” to use. Do you get the feeling that the diagram is complicated and, by looking at the diagram you start to feel a slight headache? Well, I agree, but at the same time, I must inform you that this is a “minimized version” of the Autodiscover workflow. When drowning the diagram, I have dropped many “parts” such as the mutual authentication process and other parts for making the diagram more digestible. For example, regarding the security mechanism that is implemented as part of the Autodiscover process, the Autodiscover flow description that will be provided in the next section includes a very general reference to the security flaw that is implemented.
- 5. Page 5 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 If you want to read more detailed information about the subject of security in Autodiscover environment, read the article – Autodiscover process and Exchange security infrastructure | Part 20#36 Autodiscover workflow into a non-Active Directory environment | Optional scenarios To demonstrate some of the optional Autodiscover scenarios in a non-Active Directory environment, let’s use the following organization infrastructure: The public domain name of the organization is – o365info.com The company has a public website that is published using the host name – o365info.com An external user named Bob that has the E-mail address – Bob@o365info.com , needs to create a new Outlook mail profile for connecting to his mailbox that is hosted on Exchange On-Premise server. Note – the Autodiscover method that will be implemented cannot be based on the Active Directory Autodiscover method because the Autodiscover client is located on externalpublic network, and he doesn’t have access to the organization Active Directory.
- 6. Page 6 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Scenario 1: company website that uses the public domain name | no HTTPS support The Autodiscover client (Outlook in our scenario) will take the “right part” of the recipient’s email address and will relate to the SMTP domain name as the host name of a Potential Autodiscover Endpoint. Autodiscover client will contact a DNS server and query the DNS about an IP address of a host named – o365info.com In our scenario, the DNS has an IP that is “mapped” to this hostname.
- 7. Page 7 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Note that this IP address, will point to the company’s public website that is not an Autodiscover Endpoint but the Autodiscover client doesn’t know it! The Autodiscover client uses that IP address that he gets from the DNS server and tries to check if the Potential Autodiscover Endpoint support communication using the HTTPS protocol. In this specific scenario, the company web site doesn’t support HTTPS (doesn’t have a public certificate). When the HTTPS communication test with the host o365info.com host fails, the Autodiscover Client “understand” that he will need to “move on” to the additional Autodiscover method.
- 8. Page 8 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 The Autodiscover client starts a new session, but this time; the Autodiscover client will now try to look for a Potential Autodiscover Endpoint using the host name – autodiscover.o365info.com In our scenario, an A record was created using the hostname- Autodiscover and the IP address that is mapped to this hostname point to the Exchange On-Premise server. Autodiscover client checks if the host- autodiscover.o365info.com support HTTPS. The Autodiscover Endpoint (Public facing Exchange CAS server) approves that he can communicate using the HTTPS protocol. The Autodiscover client will ask from the Autodiscover Endpoint (Public facing Exchange CAS server) to prove his identity, by providing a public certificate. In case that the server certificate was successfully verified, the Autodiscover client will send his user credentials to the Autodiscover Endpoint.
- 9. Page 9 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 The last step is the step in which the Autodiscover client asks from the Autodiscover Endpoint the required Autodiscover information for building a new Outlook Anywhere profile. Scenario 2: company website that uses the public domain name | HTTPS support The following scenario is a little confusing because, this time we deal with a public website that is mapped to the “root domain name” + support HTTPS. This scenario will cause the Autodiscover client to “believe” that he had found his Autodiscover Endpoint but in the reality, the host that he tries to communicate with, is not the required host. Autodiscover client will contact the DNS server looking for the hostname – o365info.com
- 10. Page 10 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 After he gets the IP address, the Autodiscover client tries to check if the host (the Potential Autodiscover Endpoint) supports HTTPS communication. In our scenario, the company website supports HTTPS communication and has a public certificate. The basic assumption of the Autodiscover Endpoint is that this is the “right host” and now; the Autodiscover client will generate a request for Autodiscover information. The request will be accepted by the host- o365info.com but this host is not an Autodiscover Endpoint, and he doesn’t “understand” the meaning of – “request for Autodiscover information”. The Autodiscover client understands that he tries to communicate with the “wrong host” and the next step is – moving forward the next Autodiscover methods in which the Autodiscover client will try to look for the Autodiscover Endpoint using a different host name –autodiscover.o365info.com
- 11. Page 11 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Scenario 3: HTTP redirection In this scenario, we will “deviate” from our original scenario that is based on Exchange On-Premise infrastructure in favor of a scenario that is common in an environment such as Office 365 and Exchange Online. In this scenario, the user mailbox is hosted on the Exchange Online server. The cloud infrastructure, doesn’t really publish hostnames using the “supposed naming convention” but instead, when the Autodiscover client “think” that he got his Potential Autodiscover Endpoint, the host redirects him to the Office 365 Autodiscover infrastructure for continuation of the Autodiscover process. In the following diagram, we can see that the Autodiscover client gets from the DNS server the IP address of – autodiscover.o365info.com When he tries to check if the Potential Autodiscover Endpoint (autodiscover.o365info.com) support HTTPS connections, he gets a negative response.
- 12. Page 12 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 The Autodiscover client will “move on” to the next Autodiscover method in which he tries to ask from the Potential Autodiscover Endpoint information about a “new name” of Autodiscover Endpoint. This method described as an HTTP redirection because the host redirects the Autodiscover client to “additional Potential Autodiscover Endpoint”
- 13. Page 13 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 In the following diagram, we can see that the Autodiscover client addresses the host-autodiscover.o365info.com using the HTTP protocol instead using the standard HTTPS protocol. Because the Office 365 host is “aware” to the process in which he needs to redirect the Autodiscover client to other Potential Autodiscover Endpoint, the Office 365 host send the hostname- autodiscover.outlook.com in the redirection response. Autodiscover client will try now to communicate with the “new Autodiscover Endpoint named-Autodiscover-s.outlook.com using the HTTPS protocol (I have dropped the DNS name resolution process). In the Office 365 environment the Autodiscover flow, will not end at this point, but for the time being, I will end our scenario in this phase.
- 14. Page 14 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 The Autodiscover client verifies if the “new Autodiscover Endpoint” can communicate using HTTPS and if the answer is “yes”, the Autodiscover process will continue from this point. Scenario 4: looking for an Autodiscover SRV record The following scenario, describe a special Autodiscover method that is based on a special DNS record, the SRV record. The use of the SRV Autodiscover method enables to implement the Autodiscover method in a non-Active Directory environment that is very similar to the Autodiscover method in an Active Directory environment. Until now, the Autodiscover method that the Autodiscover client use, was based on a method in which the Autodiscover client “generate” or guess the Autodiscover Endpoint name by using the “right part” from the recipient E-mail address (the SMTP domain name). In a scenario in which a specific organization owns multiple public domains, the IT needs to configure the required DNS record for each of the domains and in
- 15. Page 15 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 addition, add the name of the Autodiscover host for each of the domains to the server public certificate. Using the option of the SRV record, unable to “point” mail client that uses a different SMTP domain name to a – “single point of authority” meaning, an Autodiscover Endpoint that can serve the different client. For example, the DNS SRV record can point a recipient from the domain – o365info.com + the domain o365info.org to the one Autodiscover Endpoint named – mail3.otherdomain.com It’s important to emphasize that the SRV Autodiscover method is the “last Autodiscover method on the list”. Only if the Autodiscover client drains out all the Autodiscover methods, which we review in the former scenarios, only, then he will try to use the SRV Autodiscover method. There could be a couple of scenarios, which will “lead” the Autodiscover client to use the SRV Autodiscover method. In this scenario, the Autodiscover client tries to query the DNS server for the IP address of the hosts – o365info.com and autodiscover.o365info.com The A record for this host was not added to the DNS deliberately. The intention was to “enforce” the Autodiscover client to “fail back” to the SRV Autodiscover method. The next step of the Autodiscover client is – to query the DNS for an Autodiscover SRV record. In our example, the SRV record was a created and was configured with the host named –mail3.otherdomain.com The Autodiscover client will try to get the IP address of the host – mail3.otherdomain.com When the Autodiscover finds the host, he will try to verify that the host can communicate using HTTPS and so on.
- 16. Page 16 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 Another passable scenario is a scenario in which the Autodiscover client finds information about a Potential Autodiscover Endpoint named- autodiscover.o365info.com The “problem” is that this host doesn’t respond to an HTTPS communication request and additionally, cannot relate to the HTTP redirection request of the Autodiscover client.
- 17. Page 17 of 17 | Autodiscover flow in an Exchange on-Premises environment | non-Active Directory environment| Part 2#3 | Part 27#36 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 In this case, the Autodiscover client will “revert” to the Autodiscover method of trying to query the DNS server about an SRV record.