Hello James,

This should do it...
Dim n As Long

    n = InStrRev(ActiveWorkbook.Name, ".")
    
    ActiveWorkbook.SaveAs Filename:= _
        "C:\Users\user\Documents\Emails\5Milla\Full Email File_1.csv_Pieces\" _
        & Left(ActiveWorkbook.Name, n) & "txt" _
        , FileFormat:=xlText, CreateBackup:=False