outlook-slack-webhook-sample.vba

'
Dim WithEvents mySentItems As Items
'
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
    Set mySentItems = Session.GetDefaultFolder(olFolderSentMail).Items
End Sub
'
Private Sub mySentItems_ItemAdd(ByVal Item As Object)
    If TypeName(Item) = "MailItem" Then
        Dim objMail As MailItem
        Set objMail = Item
        TargetURL = "https://hooks.slack.com/services/..."
        Set HTTPReq = CreateObject("WinHttp.WinHttpRequest.5.1")
        HTTPReq.Open "POST", TargetURL, False
        HTTPReq.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
        Dim sendText As String
        sendText = "payload={""text"":""件名: " & objMail.Subject & "\n本文: " & Left(objMail.Body, 200) & """}"
        HTTPReq.Send (sendText)
        objMail.Close olSave
    End If
End Sub