We are making a change to our suppression systems of which you should be aware. The SocketLabs On-Demand automatic suppression system dramatically increases your deliverability by automatically blocking email to addresses which have previously hard bounced or previously complained about one of your mailings.

This year we are reinforcing our email delivery infrastructure to make it more dependable than ever. These improvements require that we change the way we handle your attempts to deliver email to addresses that are on your suppression list.

Currently if you attempt to send email to an address that is on your suppression list, we reject your attempt at the SMTP level. That is, we refuse to accept the message from your application. Beginning on February 15th, 2011, we will no longer reject these messages at the SMTP level. The new behavior for our servers will be to fully accept the messages from your sending application, and then log and delete the message without delivering it. In the end – the result is the same.

This change will not impact the effectiveness of our suppression system and it will allow us to log more information about the messages that are suppressed, such as the message and or mailing id. However, if your applications depend on having suppressed messages blocked at the SMTP level, you will have to make whatever changes you deem necessary on or before February 15th, 2011 to accommodate for this change. Suppressed messages are treated like any other message delivery failure, and can be viewed with the other failure data from the SocketLabs On-Demand Control Panel or through our API. We suggest that you access this data regularly and use it to keep your local address lists clean.