Add external access for Lync

When trying to make a Lync IM

When contacting your support team, reference error ID 1002 (source ID 243). Troubleshooting information is available online, including best practices for using Lync.

In Office 365 Plan E3

  1. Lync Admin Center
  2. Organisation
  3. External communications must turn this on

The other organisation must also have this setting on:

This message wasn’t sent because <recipient>doesn’t have permissions on your organization’s network, or because the address is incorrect. Please contact your support team.

Setting up Microsoft Lync from Office 365

After installing Lync on my 64-bit PC using 64-bit intall it would not connect.

Cannot sign in because the server is temporarily unavailable. If the problem continues contact your support team

Solved with the steps on this site:


Configure the Lync settings

  1. In the upper-right area of Lync 2010, click the Gear icon to open the Options page.
  2. In the Lync – Options dialog box, click Personal.
  3. Next to the sign-in address, click Advanced.
  4. Make sure that Manual Configuration is selected and that the configuration values are exactly as follows:

Internal server name or IP address:
External server name or IP address:

I did not need to change the firewall. So any changes I had tried, I reversed and removed.