This solution applies to all Email Security Gateways.
During a firmware update, the Email Security Gateway will undergo a quick reboot.
During this time, the MTA (Mail Transfer Agent) will be restarted. If the MTA is not listening on port 25, a connecting server would receive a "Connection Refused". As a result, they would retry at their next scheduled retry interval (this is an independent value based on the sending server's configuration).
To control this process a little more, you could go to the Basic > Administration page and take the box offline (by clicking the Offline button) prior to upgrading the firmware. This will:
- Help make sure mail does not get lost.
- Speed up the upgrade process.
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