Verify a Yahoo! Domain

If your domain registrar is Yahoo!, follow these procedures to verify your domain:

    * Gather your information.
    * Create an alias at your domain registrar.
    * Confirm the verification.

Note
You only have to add and verify a domain one time. If someone else in your company has already added and verified a domain, an error will be generated if you try to add that domain again.
To gather your information

   1.Open the Microsoft Online Services Administration Center , click the Users tab, and then click Domains.
   2. In the All Domains list, click Verify Now in the Status column of the domain that you want to verify.
   3.  In the Verify Your Domain Wizard, record the part of the Microsoft Online Services alias or host name information that comes before the first dot (similar to ms30048081), and the destination or points to address information (similar to mail.contoso.com).

      You will need this information when you create an alias at your domain registrar.

To create an alias at your domain registrar

   1. Go to http://smallbusiness.yahoo.com, and sign in.
   2.  Under Go To, click Domain Control Panel.   The Welcome to Your Domain Control Panel page opens.
   3. On the Welcome to Your Domain Control Panel page, click Manage Advanced DNS Settings. The Advanced DNS Settings page opens.
   4. On the Advanced DNS Settings page, in the A and CNAME Records section, click Add Record.
   5. In the Source box, type or paste the part of your Microsoft Online Services alias or host name information that comes before the first dot (similar to ms30048081).
   6. In the Destination box, type or paste your Microsoft Online Services destination or points to address information (similar to mail.contoso.com).
   7. Click Submit.
 If you have difficulty adding an alias to your Yahoo! account, contact the Yahoo! user support team to resolve the issue.
   8. Log off your Yahoo! account, and wait at least 15 minutes.

Note
It takes between 15 minutes and 72 hours for the alias you created on your Yahoo! account to propagate through the Internet.
To confirm the domain verification

   1.After at least 15 minutes, open the Microsoft Online Services Administration Center , click the Users tab, and then click Domains.
   2 . In the All Domains list, click Verify Now in the Status column of the domain that you want to verify.
   3. In the Verify Your Domain Wizard, click Verify.The Confirmation page of the Verify Your Domain Wizard appears, and the wizard makes a test connection to your domain to confirm that the verification was successful.
      Note
      If verification fails, the changes you made may need more time to propagate. Cancel the Verify Your Domain Wizard and come back later to verify the domain. If it has been more than 72 hours since you made the changes to your domain registrar account, log on to your account and verify that you entered the alias information correctly. If you entered the information incorrectly, you must remove the incorrect alias and create a new one with the correct information by using the procedures in this topic.
   4.Click Close to close the Verify Your Domain Wizard.
 Your domain is now listed as Verified in the All Domains pane.

After you verify your domain, you must add or migrate users and modify the domain records before users can start to send and receive e-mail. For information about how to add or migrate users and about how to modify domains, see About Using Your Domain with Microsoft Online Services.
Important
If the domain you are verifying was previously owned by another Microsoft Online Services customer, you must wait 24 hours after verifying before you add users, contacts, or distribution lists to your new domain. This prevents possible access to this information by the previous domain owner.
source:
http://www.microsoft.com/online/help/en-us/helphowto/920e7ac4-b4c5-4c06-9b9f-5e0683d0ccab.htm