[in] Index number of the attachment to delete. This is the value for the attachment's PR_ATTACH_NUM (PidTagAttachNumber) property.
[in] Handle to the parent window of any dialog boxes or windows this method displays. The ulUIParam parameter is ignored unless the ATTACH_DIALOG flag is set in the ulFlags parameter.
[in] Pointer to a progress object that displays a progress indicator. If NULL is passed in lpProgress, the message store provider displays a progress indicator using the MAPI progress object implementation. The lpProgress parameter is ignored unless the ATTACH_DIALOG flag is set in ulFlags.
[in] Bitmask of flags that controls the display of a user interface. The following flag can be set:
Requests the display of a progress indicator as the operation proceeds.
Before calling DeleteAttach, call the IUnknown::Release method for the attachment and each of its streams.
Because deleting an attachment can be a lengthy process, DeleteAttach provides the mechanism that displays a progress indicator. You can request the display of a progress indicator by passing a pointer to your IMAPIProgress : IUnknown implementation or NULL if you do not have an implementation. You must also specify a window handle in the ulUIParam parameter and the ATTACH_DIALOG flag in the ulFlags parameter.