I ran into an issue where autodiscover would fail externally and I would have to manually enter the server name and the AD domain name on the device. This happened with androids, outlook on win 8, and iphones/ipads. Internally it worked fine. All tested passed on https://www.testexchangeconnectivity.com, but I still ran into the issue.
This is how I fixed it,
My environment was setup as follows:
AD Server 2012
Exchange 2013 on Server 2012
AD domain = contoso.net
Email domain = contoso.org
contoso.org is our organizations website and it is hosted elsewhere, but I have control of the DNS.
Internal dns records. all point the LAN IP address of the server
A - mail.contoso.org
A- autodiscover.contoso.org
A- owa.contoso.org
A - servername.contoso.org
All of the above point the LAN IP address of the server
External dns records
A - mail.contoso.org
CNAME- autodiscover.contoso.org ---> mail.contoso.org
A- owa.contoso.org
A - servername.contoso.org
All of the above point the public address of the server
First I added an alternative UPN suffix (contoso.org)
http://technet.microsoft.com/en-us/library/cc772007.aspx
Next I changed a test user to the new suffix
AD users and computers >username > properties > account > select the suffix from the drop down.
Tested it and everything worked. I was able to simply login to any device I tested withusername@contoso.org and the password.
To future proof this I made a quick and dirty powershell script out of a command I found on the link above and set it to run as a scheduled task nightly on one of my domain controllers
Get-ADUser -Filter * -properties homemdb | where {$_.homemdb -ne $null} | ForEach-Object ($_.SamAccountName) {$CompleteUPN = $_.SamAccountName + “@contoso.org”; Set-ADUser -Identity $_.DistinguishedName -UserPrincipalName $CompleteUPN}"The above script:
· Gets all users with something in their homemdb attribute (i.e. mailbox users)
·
Creates a temporary variable called $completeUPN which is a
combination of every user’s samaccountname plus @contoso.com
· Sets each user to this new upn"
I hope this helps someone, because I was banging my head against the wall for while trying to figure this out.