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500 Firewall error

Description

Customers sending email through the outbound email security service receive a non-delivery report showing an error as below:

Generating server: exchange.customer.local

recipient@example.com
mr34.theemaillaundry.net #500 Firewall Error ##

Solution

This issue is happening due to restrictions in a Cisco firewall on the sending side network.

The firewall is interfering with the SMTP conversation between the sending client and recipient server.

In order to resolve the issue and allow the emails to be sent out, it is necessary to disable ESMTP/SMTP inspection on the Cisco firewall. This can be achieved by the following:
On the firewall, run ‘show run’ to identify the ESMTP/SMTP inpect rules
Disable the ESMTP/SMTP rules by inserting ‘no’ at the beginning of the line. Example are below:
no ip inspect name TEST smtp
no ip inspect name TEST esmtp

in Email Security

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