Reverse DNS lookup failed
Since this morning, for some emails that are being sent out from our office (exchange 2007 to brightmail appliance) we get this bounce back:
#< #5.0.0 smtp; 550 Host-Lookup-Failed: Reverse DNS lookup failed for 18.104.22.168 (failed)> #SMTP#
the .166 ip is our brightmail gateway and if i look in the message audit logs of the gateway i see this: Message rejected by MTA.
The mx records are set correct to the .166 IP so i dont understand why most mails deliver fine but some get this msg suddenly.