In this scenario, if an incoming call isn't answered, the call isn't transferred to Exchange Online Unified Messaging voice mail as expected. Instead, the person who is calling you hears a fast busy tone. The call never is transferred to voice mail.
- In a web browser, go to https://www.testconnectivity.microsoft.com/?testid=O365LyncDns.
- Select Office365 Vanity/Custom Domain Name Settings Test for Lync. and then click Next.
- Type the sign-in address that you use for Skype for Business Online, type the CAPTCHA text, click to select the check box to agree to the terms, and then click Perform Test.
- Review the results, and make sure that the _sipfederationtls._tcp.<domain>.com DNS SRV record resolves successfully and is configured correctly.
The following is an example screen shot of the results of the test:
Article ID: 2781465 - Last Review: Dec 28, 2016 - Revision: 1