Need urgent help. Got issue with email being rejected. getting reason given below on my barracuda.
451 Internal resource temporarily unavailable.
501 5.1.7 Bad sender address syntax( barracuda shows as the ip being in greylist)
I am trying to do telnet the recepient mail server and still get the same message. Please advice if this is a trouble on our side or the recepient and how can this be fixed.
Also have issues with email delivery being delayed. Could this be anything to do with the DNS. my firewall only has one DNS entry in it. should i add the remaining dns servers also for our ISP?
Also is it recommended to add the google dns 188.8.131.52 to the infrastructure DC for forwarders and also on the firewall.
All trouble recently started. The environment has been stable and havent had issues so far. so a bit panicky.
My exchange is 2007 sp2 with two nodes on ccr and two hub transport servers which forward the email to barracuda. Outgoing everything is allowed from trust to untrust on my juniper firewall.