Code is pretty long, but see below, the problem area is in

   .Range("AI3:AI4").Cells.SpecialCells(xlCellTypeConstants)
       If cell.Value Like "?*@?*.?*" Then
           strto = strto & cell.Value & ";"

This is where is obtains an e-mail address (which on my sheet are
valid). It has worked fine in the past but now its suddenly thrown up
this error

Sub Mail_New_Version()
   Dim FileExtStr As String
   Dim FileFormatNum As Long
   Dim Sourcewb As Workbook
   Dim Destwb As Workbook
   Dim TempFilePath As String
   Dim TempFileName As String
   Dim OutApp As Object
   Dim OutMail As Object
   Dim sh As Worksheet

   With Application
       .ScreenUpdating = False
       .EnableEvents = False
   End With

   Set Sourcewb = ActiveWorkbook

   Sheets("E-Figures").Visible = True
   Sheets("E-Access").Visible = True

   Sheets("E-Figures").Select
   ActiveSheet.Unprotect Password:="123"

   'Copy the sheets to a new workbook
   Sourcewb.Sheets(Array("E-Figures", "E-Access", "Rules")).Copy
   Set Destwb = ActiveWorkbook

   'Determine the Excel version and file extension/format
   With Destwb
       If Val(Application.Version) < 12 Then
           'You use Excel 97-2003
           FileExtStr = ".xls": FileFormatNum = -4143
       Else
           'You use Excel 2007
           'We exit the sub when your answer is NO in the security
dialog that you only
           'see  when you copy a sheet from a xlsm file with macro's
disabled.
           If Sourcewb.Name = .Name Then
               With Application
                   .ScreenUpdating = True
                   .EnableEvents = True
               End With
               MsgBox "Your answer is NO in the security dialog"
               Exit Sub
           Else
               Select Case Sourcewb.FileFormat
               Case 51: FileExtStr = ".xlsx": FileFormatNum = 51
               Case 52:
                   If .HasVBProject Then
                       FileExtStr = ".xlsm": FileFormatNum = 52
                   Else
                       FileExtStr = ".xlsx": FileFormatNum = 51
                   End If
               Case 56: FileExtStr = ".xls": FileFormatNum = 56
               Case Else: FileExtStr = ".xlsb": FileFormatNum = 50
               End Select
           End If
       End If
   End With

   '    'Change all cells in the worksheets to values if you want
   '    For Each sh In Destwb.Worksheets
   '        sh.Select
   '        With sh.UsedRange
   '            .Cells.Copy
   '            .Cells.PasteSpecial xlPasteValues
   '            .Cells(1).Select
   '        End With
   '        Application.CutCopyMode = False
   '        Destwb.Worksheets(1).Select
   '    Next sh

   'Save the new workbook/Mail it/Delete it
   TempFilePath = Environ$("temp") & "\"
   TempFileName = "Part of " & Sourcewb.Name & " " & Format(Now, "dd-
mmm-yy hh-mm")

   ActiveWindow.TabRatio = 0.908

   Set OutApp = CreateObject("Outlook.Application")
   OutApp.Session.Logon
   Set OutMail = OutApp.CreateItem(0)

   Sheets("E-Figures").Activate
   Range("A1").Select

   For Each cell In ThisWorkbook.Sheets("E-
Figures").Range("BJ1:BJ18")
   strbody = strbody & cell.Value & vbNewLine
   Next

   For Each cell In ThisWorkbook.Sheets("E-Figures") _
   .Range("AI3:AI4").Cells.SpecialCells(xlCellTypeConstants)
       If cell.Value Like "?*@?*.?*" Then
           strto = strto & cell.Value & ";"
       End If
   Next
   strto = Left(strto, Len(strto) - 1)