Our email setup was working fine until a few months ago. We then noticed that emails sent before about 10am were received straight away and after about 4pm. Between those times email often came in delayed but a failure message was received by the sender.
Running the Exchange Remote Connectivity Analyzer returned: Testing TCP port 25 on host mail.ourdomain.co.uk to ensure it's listening and open. The specified port is either blocked, not listening, or not producing the expected response.
This message coincided with the times - before 10am and after 4pm - all fine.
Exchange is listening on port 25, port 25 is allowed in through the firewall. I can't see any services running here which coincide with those times and would jump in and steal port 25.
Strangely, just before Christmas, the email was working fine all day. The Remote Connectivity Analyzer reported no problems. Now, today, we're back to port 25 problems again and no email during the day.
