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Emergency Email Maintenance - Thursday 4th October 6:00pm-7:00pm
Posted on: Thursday 4 October 2007, 17:02
Maintenance Window:-
Thursday 4th October 6:00pm-7:00pm.
Services Affected:-
Email.
Duration of expected customer impact:-
Approximately 1 hour.
Detailed description of work to be performed:-
Connections to our email platform from spam originating from non-reversible DNS addresses, are reaching the stage where left unattended they could cause a service-wide issue.
To avoid this happening we will be making some changes to the ACL configuration of our email servers. This work is aimed at deferring email sent to our customers from hosts with missing reverse DNS entries. Our current mail implementation uses something called 'Sender Verify' and will already be blocking many of these messages based on invalid return paths. What we now need to do is address the messages that have been sent from valid return addresses but originated from badly configured mail servers, compromised Windows machines or botnets. This email which almost entirely originates from spam sources constitutes a very large volume of the email handled by our mail servers and it's important we begin to address this problem to preserve the integrity of the mail platform.
http://en.wikipedia.org/wiki/Access_control_list
http://exim-www.meulie.net/exim-html-3.00/doc/html/oview.html#SEC21
http://en.wikipedia.org/wiki/Reverse_DNS_lookup
http://en.wikipedia.org/wiki/Botnet
Expected customer impact:-
At the moment email from IP addresses with no rDNS entries will be accepted by our email platform and delivered. The main difference following the completion of the work should be a marked decrease in the volume of spam messages accepted and delivered to customers by our email platform. It does mean that in rare instances legitimate email the customer is used to receiving will also be rejected. Probably the most common occurrence of this happens when a server administrator has forgotten to give their server a DNS entry. This means that emails generated by their website or forum for example will not arrive in customers' mailboxes. This can be easily fixed by the owner of the server that generated the email. The following RFC contains details regarding the correct DNS configuration of a server:-
http://tools.ietf.org/html/rfc1033
Other Notes:-
Some customers will be aware that we recently implemented ACL blocking on our mail platform however took the decision to roll the changes back:-
http://usertools.plus.net/status/archive/1190742288.htm
It's important to note that this work, whilst similar in nature, is expected to have only a fraction of the impact of the previous roll-out which involved far more validation than a simple rDNS lookup. We saw very few complaints following the previous roll-out that were due to missing rDNS records.
As always we welcome discussion surrounding this topic over on our Community Site forums:-
http://community.plus.net/forum/index.php/topic,1989.new.html
Kind Regards,
Bob Pullen
Customer Support
Thursday 4th October 6:00pm-7:00pm.
Services Affected:-
Email.
Duration of expected customer impact:-
Approximately 1 hour.
Detailed description of work to be performed:-
Connections to our email platform from spam originating from non-reversible DNS addresses, are reaching the stage where left unattended they could cause a service-wide issue.
To avoid this happening we will be making some changes to the ACL configuration of our email servers. This work is aimed at deferring email sent to our customers from hosts with missing reverse DNS entries. Our current mail implementation uses something called 'Sender Verify' and will already be blocking many of these messages based on invalid return paths. What we now need to do is address the messages that have been sent from valid return addresses but originated from badly configured mail servers, compromised Windows machines or botnets. This email which almost entirely originates from spam sources constitutes a very large volume of the email handled by our mail servers and it's important we begin to address this problem to preserve the integrity of the mail platform.
http://en.wikipedia.org/wiki/Access_control_list
http://exim-www.meulie.net/exim-html-3.00/doc/html/oview.html#SEC21
http://en.wikipedia.org/wiki/Reverse_DNS_lookup
http://en.wikipedia.org/wiki/Botnet
Expected customer impact:-
At the moment email from IP addresses with no rDNS entries will be accepted by our email platform and delivered. The main difference following the completion of the work should be a marked decrease in the volume of spam messages accepted and delivered to customers by our email platform. It does mean that in rare instances legitimate email the customer is used to receiving will also be rejected. Probably the most common occurrence of this happens when a server administrator has forgotten to give their server a DNS entry. This means that emails generated by their website or forum for example will not arrive in customers' mailboxes. This can be easily fixed by the owner of the server that generated the email. The following RFC contains details regarding the correct DNS configuration of a server:-
http://tools.ietf.org/html/rfc1033
Other Notes:-
Some customers will be aware that we recently implemented ACL blocking on our mail platform however took the decision to roll the changes back:-
http://usertools.plus.net/status/archive/1190742288.htm
It's important to note that this work, whilst similar in nature, is expected to have only a fraction of the impact of the previous roll-out which involved far more validation than a simple rDNS lookup. We saw very few complaints following the previous roll-out that were due to missing rDNS records.
As always we welcome discussion surrounding this topic over on our Community Site forums:-
http://community.plus.net/forum/index.php/topic,1989.new.html
Kind Regards,
Bob Pullen
Customer Support