I've been dealing with this for a while and I've got something that works for me, so I figured I'd pass it along:
Microsoft recently moved their Outlook.com accounts to Office 365, enabling the full Exchange experience for consumer mailboxes. Instead of connecting as an Exchange Activesync mailbox, you can now connect as a Microsoft Exchange mailbox. The problem is Outlook 2016 requires autodiscovery to configure Microsoft Exchange mailboxes, but when using a non-Microsoft alias with your account, autodiscovery looks to the domain of your alias instead of Microsoft's servers. This site explains the change and gives some good information as well as some possible workarounds: https://support.office.com/en-us/article/Reconnect-Outlook-2016-or-Outlook-2013-to-Outlook-com-for-uninterrupted-email-access-cda1751d-9503-40bf-bf76-e79454ac5eb3 However, this site is what most of this tip is based on: https://www.howto-outlook.com/howto/autodiscoverconfiguration.htm This will enable Outlook 2016 to configure your mailbox as a Microsoft Exchange mailbox, enabling the new goodness of the new Outlook.com by overriding the default autodiscover functionality. It does require that Outlook is already configured with an account. This will be the case if you've already configured Outlook to use Exchange Activesync with your account. The basic idea is to redirect to Microsoft's servers and then modify their response before Outlook uses it. 1. Create a redirecting autodiscover.xml file stored locally. I put mine in C:\save\autodiscover.xml. It should look like this: ------------SNIP------------ <?xml version="1.0" encoding="utf-8" ?> <Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/responseschema/2006";> <Response xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a";> <Account> <AccountType>email</AccountType> <Action>redirectUrl</Action> <RedirectUrl>https://autodiscover-s.outlook.com/Autodiscover/Autodiscover.xml</RedirectUrl> </Account> </Response> </Autodiscover> ------------SNIP------------ Note the <RedirectUrl> tag. It says to get the autodiscovery information for your alias at outlooks server. 2. Add a local autodiscover entry to the registry for the custom domain. This is a .reg file that creates the entry: ------------SNIP------------ Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover] "aliasdomain.com"="c:\\save\\autodiscover.xml" ------------SNIP------------ Here, I'm telling outlook to not try to find the autodiscover.xml file for aliasdomain.com on the internet through DNS and what not, but instead look to the file created in step one. You should substitute aliasdomain.com for whatever is after the @ in your alias. Note the double backslashes in the path - this is the escape method used by reg files. 3. In Outlook, try adding your mailbox. As mentioned above, you need to have an existing mailbox configured. The reason is the response received from autoconfigure is slightly incorrect and with no existing accounts, Outlook will just error out. But, with an existing account, you'll be prompted to restart Outlook. After adding your account, you'll be prompted for credentials. Use your alias and password. When Outlook prompts you to restart it, exit Outlook, but don't start it yet. 4. Now, open C:\Users\%username%\AppData\Local\Microsoft\Outlook. You should see a recently created .txt file. This is the autodiscover response. Open it and it should look like xml content. Look for the <AutoDiscoverSMTPAddress> tag. In this tag, you'll have an address like "[email protected]" This is the line you need to edit. Change the outlook address to your alias. I think what's happening here is Microsoft is replying with an internal mailbox name, but when Outlook tries to use it, it can't be found. Since this seems to be a known issue as noted in the first link above, my guess is they'll eventually change it so the autodiscover response contains the primary alias on the account. If you control the alias domain, you also might be able to change autodiscover entry in DNS to point to Microsoft's servers, but this obviously won't work if you're using a gmail address as an alias.
