To track down whether your Autodiscover DNS settings are set up to work with Office 365 email after you’re upgraded, you can use the Remote Connectivity Analyzer (RCA) tool. If you have more than one email domain, repeat these steps to test and fix issues for each domain that you use with Office 365 email.

Step 1: Get the list of email domains in your Office 365 account

Sign in to Office 365 as an admin, and go to Admin > Office 365 > Domains. You'll see a list of all the domains for your account.

Step 2: Sign in to the RCA tool and run the test

For each email domain listed in your Office 365 account , do the following to check the Autodiscover record.
 
2. Select the Office 365 tab.
3. Choose Outlook Autodiscover, and then click Next.
4. Test the first domain: In the Email address field, type a valid email address with your Office 365 service that includes the domain you're testing. You’ll use a different email address for each Office 365 domain.
Type the user name and password of an Office 365 global administrator for your account.
If you don’t know what Ignore Trust for SSL means, don’t check that box.
Check the I understand box, fill in the Captcha verification, and click Verify.
Finally, click Perform Test in the bottom right-hand corner of the screen.
5. The Remote Connectivity Analyzer runs for a few moments, performing diagnostic tests.
6. Check the results.
  • If Autodiscover is set up correctly, you'll see a result similar to this:
  • If Autodiscover is not set up correctly, your results will look like this:

Step 3: Fix missing or incorrect Autodiscover records

1. View the correct DNS record settings for each of your email domains in the Office 365 portal, specifically the CNAME record for Autodiscover under Exchange Online.
2. Update the record at your DNS hosting provider. In the instructions for create DNS records for DNS hosting providers, find the provider where you manage your DNS records. Click the link for your hosting provider to open a topic with step-by-step instructions for that provider. 
3. In the topic, go the section for updating Exchange Online records.
4. Use the correct settings for your domain (that you found above, in the portal) to update or verify the domain’s Autodiscover record: the CNAME record for Exchange Online. It should be set to: autodiscover.outlook.com.
While you should take this opportunity to check all of your DNS settings, you specifically need to make sure you have a CNAME record that reads Autodiscover.outlook.com.
Remember: you need to follow the steps to test and, if needed, update Autodiscover for each custom domain in your account.

Frequently Asked Questions

Is there anything else I can do to keep Outlook working with Office 365 after the service upgrade?
Yes, there are two things you should consider doing:
  1. Test your Mail Exchanger (MX) DNS records. These records make sure that email from people outside your organization make it to Office 365. If an MX record is misconfigured, email from people outside your organization may stop arriving.

    The simplest way to check this is by going to https://testconnectivity.microsoft.com and running the tests for Office 365 Exchange Domain Name Server (DNS) Connectivity Test on the Office 365 tab.
  2. Make sure that your Outlook client has the latest updates from Microsoft. The easiest way to do this is by running Windows Update.        
We received the Office 365 service upgrade, and now can’t connect to Exchange Online from Outlook. What should we do? 
First, use the Remote Connectivity Analyzer tool to help you correct settings with the Autodiscover CNAME records. In many cases, this is sufficient to fix connectivity problems.
If correcting your Autodiscover records isn’t the solution, try repairing one of your Outlook profiles. If this works, have other users repeat this step.
You should not have to create a new Outlook profile, except as a last resort.
If you need immediate assistance, please go to the Support Overview page in the Microsoft Online Portal to find the right resource—you’ll see several options listed under “Quick solutions for common issues.”
How can I get help with this? 
You can create a service request to get assistance from Office 365 Technical Support: our support engineers can assist you with the connectivity tool and resolving any issues identified.
You will need to know who your DNS hosting provider is, and have the user name and password to your organization’s account on their website. Having this information will make it easier for Office 365 support engineers to help you quickly.
What’s an email domain? 
An email domain is the part of an email address followed by the @ sign. For example, if your email address is michael@contoso.com, then contoso.com is your email domain.
How can I tell what domains I use with Office 365?
Sign in to Office 365 as an admin, and go to Admin > Office 365 > Domains. You'll see a list of all the domains for your account.
How do CNAME records and Autodiscover help Outlook connect to Office 365? 
To connect Outlook to Office 365, you should just be able to type in your email address and password in Outlook on your desktop, and let Outlook do the rest. When Autodiscover is set up with the correct CNAME record, Outlook and Office 365 can work together to do this for you.
Without Autodiscover, however, Outlook needs a complex value (resembling 12345678-90AB-CDEF-1234-567890ABCDEF@contoso.com) that is different for each Office 365 user. Even with this value, Office 365 features such as Out of Office messages and free/busy information will not be available to users who connect to Exchange Online by using a method other than Autodiscover.
We don’t use Autodiscover. Can we keep manually configuring Outlook to connect to Exchange Online? 
Without Autodiscover, Office 365 features such as Out of Office messages and free/busy information will not work.
Office 365 only supports connections to the Exchange Online service via Autodiscover. While manually configuring Outlook to connect to Exchange Online may work with Office 365, it is not supported. You should understand there is a risk you will periodically lose all connection to the service without notice or warning, and may need to recreate all Outlook profiles to resolve connectivity issues.
Can we keep connecting to Exchange Online using the Exchange Server’s “POD” number? 
No.
The connectivity tool is asking me to create a CNAME record, but my DNS hosting provider doesn’t support this. What should I do? 
Try calling your hosting provider. Even if you can’t create this record on your own, your provider may be able to do it for you.
If your provider can’t create the record, please call Office 365 Technical Support.
We have both internal and external DNS records. Do both have to be configured correctly for Autodiscover to work properly? 
Yes.
The connectivity tool is telling me to change my MX (Mail Exchanger) record from mail.global.frontbridge.com, which Office 365 told me to use when I first set up my service. Do I need to do this? 
Office 365 has deprecated “generic” MX records like this and will end all support for these records in July 2013. You should change these records immediately. Learn more.
Examples of generic MX records include mail.global.frontbridge.com and mail.messaging.microsoft.com.