You don't need to expand the list in order to establish whether it contains an e-mail address. All you need are the name of the list and the e-mail address to find and then the following 'InDistList' function will establish whether the address is in the list. olListMember can be an e-mail address or a domain. If you want to check all lists, you can lose ', sDistListName as String' and the condition that relates to it:
Function InDistList(olListMember As String, sDistListName As String) As Boolean
Dim olNS As Outlook.NameSpace
Dim olFolder As Outlook.Folder
Dim olDistList As Outlook.DistListItem
Dim olFolderItems As Outlook.Items
Dim sList As String
Dim x As Integer
Dim y As Integer
Dim iCount As Integer
Set olNS = GetNamespace("MAPI")
Set olFolder = olNS.GetDefaultFolder(olFolderContacts)
Set olFolderItems = olFolder.Items
iCount = olFolderItems.Count
sList = ""
For x = 1 To iCount
If TypeName(olFolderItems.Item(x)) = "DistListItem" Then
Set olDistList = olFolderItems.Item(x)
If olDistList.DLName = sDistListName Then
For y = 1 To olDistList.MemberCount
If InStr(1, olDistList.GetMember(y).Address, olListMember) Then
InDistList = True
Exit For
End If
Next y
End If
End If
Next x
lbl_Exit:
Set olNS = Nothing
Set olFolder = Nothing
Set olFolderItems = Nothing
Exit Function
End Function