Issue Definition: On the o14 MOP portal, while trying to create a new user as an administrator, there is
an option to enter alternate email address. When we  try to add a non *.onmicrosoft.com email account , which is registered as a vanity domain. This
email address is considered as Office 365 email address and the process does not go through.

 

Assessment:

 When you setup and integrate your on-premise domain with online, the address space gets registered. Hence any email address with
this alternate domain address space is considered O365 email address. This is the correct behavior, if we had an exchange online mailbox setup. However,
since the domain purpose of this vanity domain is just SharePoint, you should be able to use your on-premise address as alternate email address. This is a by
design behavior. However, the workaround available to meet this requirement is
:

 

We will need to the use the Windows Azure powershell
for the same.

 

1. Login to windows azure powershell

2. Get the UserPrincipalName for the account for which
he wants to change alternate email address.

3. Run on the command : Set-MsolUser
-UserPrincipalName user@yourdomain.onmicrosoft.com
-AlternateEmailAddresses user2@yourvanitydomain.onmicrosoft.com

Alternateemailaddresses can be your vanity domain email address also.

 You can download and install the windows azure PowerShell from here:

http://technet.microsoft.com/en-us/library/jj151815.aspx