Information Technology Services

Going Digital with Joey Brenn

Closing Port 25 prevents outbound SPAM

by Joey Brenn | Nov 04, 2013

Information Technology receives alerts from our internet vendor, AT&T, about suspicious activities seen coming from our network.  The latest one concerns a system on our network that has been compromised and is sending out SPAM email messages.  These are not new occurrences but we have gotten quite a few in recent weeks and our efforts to find the machine in question has been fruitless.  The machine appears for a short period of time and then disappears from the network.  It seems to come on to our network during evening times and stays for about an hour or so.  In order to comply with our agreement with AT&T and to be good citizens of the Internet, we have blocked all outbound SMTP Protocol (Port 25) from leaving our network unless it is going through our email servers.  This did not affect our email servers and in no way impacts the flow of normal email.  This move prevents us from getting placed on the SPAM sender databases, causing us an interruption in email flow.  If you have any questions, please send an email to

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