Wird vermutlich am Filter-Ausdruck liegen?

Versuch mal so:

Option Explicit

Sub Test()
  
  Dim folder1 As Outlook.Folder
  Dim folder2 As Outlook.Folder
  
  Set folder1 = ...
  Set folder2 = ...
  
  Dim strFilter As String
  strFilter = CreateDateTimeFilter(DateSerial(2022, 12, 1), DateSerial(2022, 12, 31))
  
  Dim objItems As Outlook.Items
  Set objItems = folder1.Items.Restrict(strFilter)
'  Set objItems = folder2.Items.Restrict(strFilter)
  
  Dim colAllMailItems As VBA.Collection
  Call AddMailItemsFromItems(objItems, colAllMailItems)
  
  Dim objMailItem As Outlook.MailItem
  For Each objMailItem In colAllMailItems
    ' folder-name, mail-subject
    Debug.Print objMailItem.Parent.Name, objMailItem.Subject
  Next
  
End Sub

Public Function CreateDateTimeFilter(DateFrom As Date, DateTo As Date)
  Const OL_RESTRICT_DATETIME_FORMAT = "ddddd h:nn AMPM"
  CreateDateTimeFilter = _
    "[SentOn] >= '" & Format$(DateFrom, OL_RESTRICT_DATETIME_FORMAT) & "' " & _
    "AND [SentOn] <= '" & Format$(DateTo, OL_RESTRICT_DATETIME_FORMAT) & "'"
End Function

Public Sub AddMailItemsFromItems(ByVal Items As Outlook.Items, ByRef MailItemCollection As VBA.Collection)
  
  If MailItemCollection Is Nothing Then
    Set MailItemCollection = New VBA.Collection
  End If
  
  Dim objItem As Object
  For Each objItem In Items
    If TypeOf objItem Is Outlook.MailItem Then
      Call MailItemCollection.Add(objItem)
    End If
  Next
  
End Sub

Hab den Code mal einfach gehalten / nur auf Folder1 bezogen.