You will need a different technique to process that subject. Assuming the ID is a whole number then:
Sub GetID()
'Graham Mayor - https://www.gmayor.com - Last updated - 21 Apr 2021
Dim strID As String
Dim olMsg As MailItem
Dim oData As MSForms.DataObject
On Error Resume Next
Select Case Outlook.Application.ActiveWindow.Class
Case olInspector
Set olMsg = ActiveInspector.currentItem
Case olExplorer
Set olMsg = Application.ActiveExplorer.Selection.Item(1)
End Select
strID = GetNum(olMsg.Subject)
If strID = "" Then
MsgBox "ID not found", vbCritical
Else
Set oData = New DataObject
strID = "id-" & strID
MsgBox strID & vbCr & vbCr & "copied to clipboard", vbInformation
oData.SetText strID
oData.PutInClipboard
Set oData = Nothing
End If
lbl_Exit:
Exit Sub
End Sub
Private Function GetNum(sText As String) As String
Dim i As Integer
For i = 1 To Len(sText)
If Mid(sText, i, 1) >= "0" And Mid(sText, i, 1) <= "9" Or Mid(sText, i, 1) = "." Then
GetNum = GetNum + Mid(sText, i, 1)
End If
Next
lbl_Exit:
Exit Function
End Function