This has nothing to do with the email server. You are distributing to people on your domain. So you need to configure a DSP (Directory Service Provider) as a DSC (Directory Service Connector). Go to QEMC --> System --> Directory Service Connectors, and configure yours (probably Active Directory). If you do this properly, you will be able to search for users in that popup box. If you want to distribute over email, you need to make sure that user has an email address associated with his AD account, otherwise you will need to add him as a Custom User. I think it would help you to read the QVS Reference Manual.