You can indicate which email account to send from, Jean-Pierre, as long as the account you use is a valid Outlook email account. (This works when using Outlook for sending emails.)

Dim oOutlook As Object, oOutlookAccount As Object
Dim varAccount as Variant

If Not IsNull(Me.FromEmailAddress) And Me.FromEmailAddress <> "" Then
        varAccount = Me.FromEmailAddress
        For Each oOutlookAccount In oOutlook.Session.Accounts
               If oOutlookAccount = varAccount Then
                     Set .SendUsingAccount = oOutlookAccount
               End If
         Next
End If

When sending batch emails, I use this code inside my send loop. The "Me.FromEmailAddress" item is a form field containing the email address to send from. This code will throw an error if it's not previously set up as a valid Outlook email account.