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Audio, video, and application sharing sessions
Data sharing sessions
Audio and video sessions
Lync mobile push notifications
Additionally, you should make sure the firewall allows Microsoft Online Services Sign-In Assistant traffic. To do this, take the following steps if you are using Microsoft Forefront Threat Manager Gateway. Similar steps can be taken for other gateways.
If you are using your own domain name with Office 365, contact your domain name registrar for details about how to make the following changes to your DNS records.
If your organization supports external communication (that is, connections with other organizations that have external communication enabled), add the following DNS Service (SRV) record as well:
If your organization’s Internet proxies or firewalls are configured to block external SRV queries, add the following CNAME entries to your internal DNS server: