This is an update to the previously reported problems resulting in occasional delays in the delivery of emails to customers' mailboxes. A copy of the last announcement can be seen here:-
http://usertools.plus.net/status/archive/1189526621.htm

Monitoring of the platform since the last Service Status posting suggests that very little incoming email is being delayed on our delivery servers, and where this is happening the mail is only being delayed for short periods of time.

Our network engineers have been conducting planned maintenance work throughout the week to fully resolve the problems that were identified as part of this investigation. This work is expected to conclude tomorrow:-
http://usertools.plus.net/status/archive/1189789775.htm

A brief summary of the changes that are being made can be found in the blog post published here:-
http://community.plus.net/comms/2007/09/11/upcoming-email-platform-changes/

Some of the changes have been to improve the blocking of email sent from hosts with suspicious DNS entries, and mail originating from dynamic IP addresses.
http://en.wikipedia.org/wiki/Reverse_DNS
http://en.wikipedia.org/wiki/Dynamic_IP#IP_address_allocation

This is an recognised and accepted spam prevention measure and is expected to significantly reduce the volume of unsolicited email that reaches customers' mailboxes.

What it also means is that email sent to customers via poorly configured mail servers or from dynamic IP addresses may be bounced back to the sender whereas before completion of this work it will have been accepted.

Where this happens the bounced emails contain an error similar to the following:

/*550 REJECTED: We do not accept email from dynamic IP's. Connection from the IP address 0.0.0.0 has been refused. If you think we have done something wrong then please forward a copy of this message complete with full email headers to abuse@plus.net*/

These changes have been in place on the secondary mail servers for a day now with little disruption. Tomorrow morning they will be introduced to the primary mail servers.

We would like to remind customers that in the vast majority of cases, the reason for the above rejection will be valid and it is the responsibility of the sending host to ensure that their mail platform is correctly configured.

During the early stages of this implementation we would like to request that any feedback or enquiries are channelled via our Community Site discussion forums:-
http://community.plus.net/forum/index.php?board=3.0

Kind Regards,

Bob Pullen
Customer Support