Plusnet Service

We have identified a problem where large numbers of connection attempts from spam sources with non-reversible DNS addresses are tying up mail server resources. These connection attempts are reaching critical levels and left unattended have the potential to cause widespread problems with our incoming mail platform.

If you were logged in to the portal, you could associate your username with this problem.

Problem has been passed to a Network Engineer for further investigation.

We need to look at blocking connection attempts from these sources. They do not originate from a specific source and have been steadily increasing over time.

Whilst Exim performs a host look up, implementing blocking here would be difficult for us without also deferring mail from hosts where there is a forward and reverse DNS mismatch which is known to have a significant impact on customers.

Suggest we defer messages in the ACL config from hosts with missing rDNS but allow messages from hosts where the forward and reverse don't match.

Change control complete and configuration changes ready for deployment. Will be rolled out once maintenance post has been published.

Now rolled to the live platform.

Monitoring suggests that the changes have improved the situation. Downgrading problem whilst we continue to monitor.