If you can’t communicate with Skype for Business (Lync) users in other organizations, or with Skype users, first verify that your organization allows communication with external contacts. If necessary, contact your workplace technical support and refer them to this guided walkthrough for admins: Set up Skype for Business (Lync) Online external communications.
If your organization does allow external Lync contacts, here are some other troubleshooting steps you can take.
Skype for Business (Lync) external contacts still show “Presence Unknown” after 72 hours
Notify your workplace technical support. You can communicate with external Skype for Business (Lync) users only if the Skype for Business (Lync) admin in both organizations has turned on external communications.
Can’t communicate with Skype contacts
Verify that the Skype user is signed in with a Microsoft account (formerly Windows Live ID).
If the Skype user has a custom Microsoft account (one that does not end in outlook.com, live.com, hotmail.com, or msn.com) you must format their IM address like this:
For example, if your Skype contact’s Microsoft account is email@example.com, enter it as
If you still can’t communicate with the Skype user after 72 hours, notify your workplace technical support, and provide them with this link: Set up Skype for Business (Lync) Online external communications.
Can’t talk to two or more Skype users at the same time
Tip: Before you send the meeting invitation, click Meeting options in the ribbon, and under Permissions, click A new meeting space (I control permissions). That way the Skype users won’t have to wait in the lobby before joining the meeting.
Can’t communicate with AOL, Yahoo!, or Google Talk users
Lync 2013 for Office 365 supports external Skype for Business (Lync) users, and Skype users signed in with a Microsoft account. Communication with other IM providers isn’t supported.
I have a Skype issue that isn’t listed here
Troubleshooting Lync-Skype Connectivity describes some of the less-common scenarios.