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Meeting invitations are not sent from Outlook in Skype for Business


Consider the following scenario:

  • You're on a computer that has Microsoft Outlook 2010 or Outlook 2013 and Microsoft Skype for Business installed.
  • The Skype for Business client has the March 8, 2016 update applied.
  • You have the Use Auto-Complete list to suggest names when typing in the To, Cc and Bcc lines option enabled in Outlook.
  • You create an online meeting, and then you select the meeting recipients from cache instead of the global address list (GAL).
  • You select the send option to send a meeting invitation.

In this scenario, you receive the following error message:

The request failed. Please try again. Make sure that you are signed in to Skype for Business.


This problem occurs because of a known issue in the KB 3114831 version of UCAddin.dll (a Skype for Business plug-in for Outlook).


To fix this problem, install the June 7, 2016 update (KB3115033) for Microsoft Lync 2013 (Skype for Business).



Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

To work around this problem, clear the Auto-Complete cache. To do this, use one of the following methods.

Method 1

Change the manner in which the Skype for Business Add-in for Outlook (UCAddin.dll) resolves recipients for meetings. To do this, create the following registry key:

Subkey location: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Lync\AddinPreference

DWord name: RecipientResolutionMode

Value data (decimal): 2

Method 2

Follow these steps:

  1. Open Outlook Options.
  2. On the Mail tab, locate the Send messages section.
  3. Clear the Use Auto-Complete List to suggest names when typing in the To, CC, and Bcc lines check box. The, click the Empty Auto-Complete List button.

More information

Still need help? Go to Microsoft Community.