I have an astaro with transparent smtp proxy. Every incoming email passes throught a router before reaching the ASG server V6. Every port of Astaro's IP on the ruter is closed except port 25.
The Astaro serves only incoming emails. When an email passes through the Astaro it is sending to a real smtp qmail server on a linux.
The problem is: some mail servers send repeating emails (sometimes an email is received several times, 7 times for an example). What could be wrong? I think that the sending mail server don't receive a confirmative message about delivering the emails.
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