Hey,

you have to cast the date since it is a data type.

For Each OutlookMail In Folder.Items
If TypeName(OutlookMail) = "MailItem" Then
If CDate(OutlookMail.ReceivedTime) >= Range("Start_of_Month").value Then
If CDate(OutlookMail.ReceivedTime) <= Range("End_of_Month").value Then