Loop through all recipients in the `MailItem.Recipients` collection. For each recipient if the `Recipient.AddressEntry` property is not null, read the `AddressEntry.Members` property (returns AddressList object). If it is not null, recursively process each member of the list.

Like this:



    Private Function GetAllRecipients(ByVal mailItem As MailItem) As List(Of String)
        Dim allRecipients As New List(Of String)
        For Each rec As Recipient In mailItem.Recipients
            If rec.AddressEntry IsNot Nothing Then
                AddAddressEntryMembers(allRecipients, rec.AddressEntry)
            End If
        Next
        Return allRecipients.Distinct.ToList()
    End Function

    Private Sub AddAddressEntryMembers(ByRef allRecipients As List(Of String),
                                       ByVal addressEntry As AddressEntry)
        If addressEntry.Members Is Nothing Then
            allRecipients.Add(addressEntry.Address)
        Else
            For Each member As AddressEntry In addressEntry.Members
                AddAddressEntryMembers(allRecipients, member)
            Next
        End If
    End Sub

To get the number of recipients just call the return the list and call `Count`:



    Dim totalRecipients = GetAllRecipients(mailItem).Count()

I'm writing an Add-In for Outlook 2010 that should get the total number of people the recieving the email.

I can get the email property fairly easily with the following code:



    Dim mailItem As MailItem
    mailItem = Globals.ThisAddIn.Application.ActiveInspector.CurrentItem

[`MailItem`][MailItem] exposes some properties like:

* [`MailItem.Recipients`][MailItem.Recipients]
* [`MailItem.To`][MailItem.To]

However, if the email is going out to a [contact group (formerly distribution lists)][group], `mailItem.Recipients.Count` will only return a value of `1`, even though multiple people will get the email.

Is there a way to query the total number of recipients within a contact group?

On some level it has to be possible, because Outlook will even do some of it for you:

![RecipientCount](http://i.imgur.com/wOVJS8r.png)


[MailItem]: http://msdn.microsoft.com/en-us/library/office/dn320330.aspx
[MailItem.Recipients]: http://msdn.microsoft.com/en-us/library/office/ff865320.aspx
[MailItem.To]: http://msdn.microsoft.com/en-us/library/office/ff860378.aspx

[group]: http://office.microsoft.com/en-us/outlook-help/create-and-edit-a-contact-group-formerly-distribution-lists-HA010354963.aspx