External users can�t join Lync Online conferences anonymously or as guests

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Problem

When you try to connect to a Microsoft Lync conference by using the Microsoft Lync 2010 Attendee client, you may experience one of the following symptoms:

Symptom 1

The attendee clicks the Join online meeting link for Microsoft Lync Online and then receives the following error in the Lync 2010 Attendee client:

Reference ID 101 (source 238)
There was a problem verifying the certificate from the server.

Symptom 2

The attendee isn't joined to the meeting with presentation capabilities such as sharing.

Symptom 3

The attendee clicks the Join online meeting link for Lync Online. However, the Lync Online client doesn't load. Instead, the Microsoft Lync Web Application loads.

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Solution

For symptom 1

To resolve symptom 1, add the necessary DNS records to resolve the issue.

Check the _sipfederationtls._tcp.domain record and _sip._tls.domain record in DNS (where the placeholder domain represents the domain suffix of your user ID). These records are required so that anonymous users outside your organization can locate and connect to the correct Lync Online servers. These records should be configured as follows:

Record Type:  SRV
Record name: _sipfederationtls
Protocol:  _tcp
Weight: 1
Priority: 100
Destination Host:  sipfed.online.lync.com
 
Record Type:  SRV
Record name: _sip
Protocol:  _tls
Port: 443
Weight: 1
Priority: 100
Destination Host:  sipdir.online.lync.com

For more information about how to configure the necessary DNS records for Lync Online, visit the following Microsoft websites:

Wiki: Ensuring your network works with Lync Online

2566790�Troubleshooting Lync Online DNS configuration issues in Office 365

For symptoms 2 and 3

To resolve symptoms 2 and 3, the user should either switch their default browser to Windows Internet Explorer or copy the Join online meeting link from their invitation and then paste it in their browser.

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More information

For symptom 1

The Lync 2010 Attendee client can't correctly locate the Lync Online servers because of missing SRV records in DNS. These records enable anonymous users to join Lync Online conferences.

For symptoms 2 and 3

The user is using Google Chrome as their default browser. The Lync Browser Helper add-in isn't configured for Google Chrome when the Lync 2010 Attendee client is installed.

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

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Still need help? Go to the Office 365 Community website.

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