Spam BYPASSING MX and hitting server direct

[Rootaah]

Our IMAIL host is claiming that spam is bypassing our MX records and hitting our mail server directly, which they are hosting.

They are claiming it cannot be stopped and we need to start living with the spam. All they can support is the Barracude filter which prevents the spam that goes through the MX.

I cannot believe this is the case. Can anyone help?

 

[niccoli]

I've seen this first hand. What we did to stop it on our servers was setup a firewall rule that only allows inbound email to come from the barracuda and deny's email from any other source.

 

[da sponge]

That's the most effective.

You can also set up relaying rules on the SMTP server and limit relaying to only the IP of the barracuda.

 

[Xipher]

I have done both, the later I have setup in Exim and it can take a little work but once you have the initial configuration done it's only a matter of updating a text file with the domains to only accept from the Cuda.