Hi Chris,
Currently, Microsoft Office 365 customers who utilize single sign-on (SSO) through AD FS 2.0 and have multiple top level domains for users' user principal name (UPN) suffixes within their organization (for example, @contoso.com or @fabrikam.com) are required to deploy a separate instance of AD FS 2.0 Federation Service for each suffix. There is now a rollup for AD FS 2.0 (http://support.microsoft.com/kb/2607496) that works in conjunction with the “SupportMultipleDomain” switch to enable the AD FS server to support this scenario without requiring additional AD FS 2.0 servers.
For more information, please refer to the following link:
http://community.office365.com/en-us/wikis/sso/support-for-multiple-top-level-domains.aspx
Have you verified the abc.com domain to Office 365?
To do further investigation, please also provide us the domain name via private message.
To read private messages, you can perform the steps below:
.Go to the your details section on the right side of the community site.
.Click Private messages.
.Click the subject title of the response to read the message.
.You can reply by using the form in this display.
.Click Submit Reply.
Thanks,
Jason Jiang