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, use one of the following methods to clear the Auto-Complete cache.
Method 1
Change the manner in which the Skype for Business Add-in for Outlook (UCAddin.dll) resolves recipients for meetings. To do so, create the following registry key:
On the Mail tab, locate the Send messages section.
Clear the Use Auto-Complete List to suggest names when typing in the To, CC, and Bcc lines check box. Then, select the Empty Auto-Complete List button.