MPP Australia Email Security Blog

Greylisting is a very effective, low-resource tool to stop spam and virus’. It works by sending an SMTP temporary failure message to any new sender on your network. Most spam drones and virus engines do not retry after temporary failure messages and simply go away, whilst legit mailservers will retry again after a period. Just be aware that new senders emails wont come through instantly – but once retried from the sending mail server and found OK their address is recorded and allowed as normal from then on.

Greylisting works with MPP and Postfix systems, and is integrated on a per group or system wide basis – and is another way that the MPP engine enables mail admins to reduce end user spam email even more.

We have been running the MPPD for a few years now to i thought it would be intersting to see the stats that the server is producing for our email filtering.

Date

Total

Clean

Virus

Spam

Error

WBL matched

RBL matched

11-19

24527

Clean 1996 (8.14%)

Virus 49 (0.20%)

Spam 2184 (8.90%)

0.00 (%)

0 (0.00%)

RBL 20298 (82.76%)

We sampled 1 days email (20 hrs) to see how it was performing – and the figures are amazing. Over 24000 emails hit our server, of which only 8% were legit! so over 22000 emails were junk – with the MPP filter blocking RBL (black list), Commtouch traced spam and ClamAV ID’d virus’ at the front door of our sendmail box. Some were rejected, some sent to SQL quarantine, and some passed through with no noticeable affect on the server boxes performance.Its incredible to think what end users would be getting in their mailbox each day if MPP wasnt there protecting the system.