If you want to get all members of to,cc, bcc fields from the current outlook compose mail item,then we can use Application.ActiveInspector().CurrentItem object in vsto add-ins.
you can try following code snippt for reading all Recipients information with address, name and we can also get to,cc, bcc fields from the current compose mail item.
Private Sub GetInfo() Dim strTo As String = "" Dim strCC As String = "" Dim strBCC As String = "" Dim _item As Outlook.MailItem = Globals.ThisAddIn.Application.ActiveInspector().CurrentItem strTo = _item.To strCC = _item.CC strBCC = _item.BCC For Each Rec As Outlook.Recipient In _item.Recipients MessageBox.Show("Recipient name : " & Rec.Name) Next End Sub