PRB: "Login has failed" Error Using the MAPISession Control

When calling the SignOn method of the MAPISession control, the following error may occur:

The LogonUI property of the MAPISession control is set to False and the UserName property of the control contains an invalid profile name or is empty.

Set the UserName Property of the MAPISession control equal to a profile name that exists on the machine before the SignOn method of the control is called.

This behavior is by design.

The MAPI 1.0 specification requires a profile to log on to a messaging session. The MAPISession control was written before the MAPI 1.0 specification was established. In order to use this control to establish a MAPI 1.0 session and prevent the Choose Profile dialog box from being displayed, the Username property must be used to pass the name of the profile needed to sign on.