Outlook distribution list hanging up on contact items query

Dim Contact As ContactItem
For Each Contact In ContactsFolder.Items
    Debug.Print Contact.CompanyName
Next

When you defined Contact as ContactItem you are telling VBA exactly what type of thing it should find in Items. This works great, only if all items in the ContactsFolder are actually ContactItems.

In other words, you are specifically going through all items in a bag but specifically making each of them an Apple - but when you encounter an Irange, VBA throws an error.

What I generally do in this situation is instead of saying that I want to go through all apples in a bag, I want to go through each item in a bag, so something like:

Dim mContact 'by not dimensioning it you basically allow mContact to become whatever type each item is 
For Each mContact In ContactsFolder.Items
    Debug.Print mContact.CompanyName
Next

Note that I changed your name to mContact because it's probable Contact is a keyword in VBA and it's sometimes better to not deal with this.

This above will still cause errors because any mContact which does not have a .CompanyName attribute.

What you can do is the following:

Dim mContact 
For Each mContact In ContactsFolder.Items
    if mContact.Class = olContact then
        Debug.Print mContact.CompanyName
    Else
        Debug.Print "Not a Contact! Actually a :" & typename(mContact)
    End if
Next

This will check for whether the object you are iterating through (the fruit from the bag) is actually an "apple" first, and if not, tell you what type of fruit it is.

In order to distinguish between Lists and Contacts, you can alter your code to the following:

Sub ContactName()

On Error GoTo ErrHandler

Dim ContactsFolder As Folder
Set ContactsFolder = Session.GetDefaultFolder(olFolderContacts)
MsgBox ("Contacts found: " & ContactsFolder.Items.Count)

Dim Contact As ContactItem
Dim distList As DistListItem
Dim i As Integer

For i = 1 To ContactsFolder.Items.Count

    If TypeOf ContactsFolder.Items(i) Is DistListItem Then
      Set distList = ContactsFolder.Items(i)
      Debug.Print distList.DLName
    ElseIf TypeOf ContactsFolder.Items(i) Is ContactItem Then
      Set contact = ContactsFolder.Items(i)
      Debug.Print contact.FullName
    Else
      Debug.Print "Item is something else"
    End If

Next i
Exit Sub

ErrHandler:
    Debug.Print Err.Description
    Stop
    Resume

End Sub

Note, I changed the property I'm accessing from CompanyName to FullName for my tests as I didn't have CompanyName for all my contacts.