I was one of the early birds running a SMG 23.4.
So I had to follow these instructions: The December SMG update will be live any minute.
But after upgrade my SMG did not listen on SMTP port. There was no inbound/outbound communication possible. After a short panic I found out that listening on all ip addresses (0.0.0.0) does not work any more after this update.
Define an explicit ip address (internal ip instead of 0.0.0.0) and your SMG will work again!
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