Recently when sending emails to various addresses I received a bounce message with the following text - “Listed on Barracuda Reputation Block List (BRBL). Host said: 554 Service unavailable; Client host blocked using Barracuda Reputation”. This almost seems like there is an Australia-wide spam filter problem, since several of the bounced messages were sent to .gov.au addresses. Can you suggest why this is happening?

Fortunately (for us) this is not an Australia-wide spam filter problem, but instead relates specifically to your ISPs mail server. Several IT security companies compile reputation block (black) lists or RBLs. These are essentially spam blacklists which list the IP address of computers which have a poor reputation, commonly due to being the originating point for email spam messages. If the IP address of your email server is listed on an RBL to which an organisation subscribes, then it is likely emails sent through your email server will be rejected by that organisation, since they consider your email server to have a poor reputation and potentially be a relay point for spam messages. Most organisations subscribe to the major RBLs so if your mail server IP address is listed on the RBL, there is unfortunately nothing you can really do to get around this issue except contact the operator of the mail server, presumably your internet service provider, and alert them to the fact the email server has been placed on an RBL. Often the ISP can speak with the RBL to get their IP address delisted but this could take time.

If you cannot wait and must send an email to an organisation that is rejecting your messages you will need to use a different outbound mail server to send the message. The easiest way to do this would be to setup a Hotmail or Gmail account and then send your message using that service. Given the popularity of both these providers, together with the number of people who use them, it is unlikely that they would be placed on any RBLs so you should be successful in sending your message. That said, it is still very important you contact your ISP to advise about the problem with the main mail server, so that you can send messages through that server in the future.