Reverse DNS Issue with Barracuda Spam Filter

Unanswered Question
Oct 23rd, 2008

Hi, I have a Barracuda Spam Filter which accepts our incoming smtp and passes it on to our Exchange Server.

For Outgoing emails the Exchange server sends directly out.

I have static Nats set up as follows (external IP's replaced)

Exchange Server

static (INSIDE,OUTSIDE) netmask


static (INSIDE,OUTSIDE) netmask

also access-lists as follows

Exchange (https & www for Outlook Web Access)

access-list OUTSIDEIN extended permit tcp any host eq https

access-list OUTSIDEIN extended permit tcp any host eq www

Barracuda (incoming SMTP)

access-list OUTSIDEIN extended permit tcp any host eq smtp

Problem is when I send emails out, it goes out as which does not match up with the MX record that points to

Therefore we are receiving Reverse DNS failures from recipients

<exchange1.ourdomain.local #5.7.1 smtp;550 5.7.1 Client host rejected: cannot find your hostname, []>

Is it possible for our Exchange Server to send out via ? (I cannot use the Barracuda as an outgoing relay)



I have this problem too.
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shaw.chris Thu, 10/23/2008 - 04:41

Thanks Andrew,

Would I need this static NAT for the Exchange Server ( rather than the Barracuda as I want the Exchange server to go out as

I do have Global Nat set up using the Interface address for all inside hosts, but neither the Barracuda or Exchange Server use that address, they currently go out using the addresses I have set up in the Static NATs




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