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Summary: You can look at the progress of a priority problem in more detail here.
Problem: [46935] Inbound Mail Delivery Status: Closed
Problem description Added on: 04/10/2007 @ 15:24

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.

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Comment updated on: 04/10/2007 @ 15:26

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

Comment updated on: 04/10/2007 @ 15:42

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.

Comment updated on: 04/10/2007 @ 15:53

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.

Comment updated on: 04/10/2007 @ 16:58

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

Comment updated on: 04/10/2007 @ 18:29

Now rolled to the live platform.

Comment updated on: 04/10/2007 @ 19:04

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

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