On Wed, 14 Jan 2009 10:52:04 -0800, Randy Klumph <[log in to unmask]> wrote:

>(only Charter.net is generating this error)

Several customers, including our own hosting servers have reported similar
problems, all with charter.net.  They must be having (or recently have had) DNS
problems that prevented reverse lookups from working, thus they rejected the
incoming email from otherwise legitimate sources.