Add external access for Lync

When trying to make a Lync IM

http://office.microsoft.com/en-gb/office365-suite-help/let-lync-online-users-communicate-outside-your-organization-HA102837606.aspx

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.