Hi,
The smtp error code following SMTP response code and information from your IronPort Appliance indicate that the sender base reputation score of the connecting smtp server are Poor and based on the configuration of your Appliance, the connection got rejected.
----- SMTP response code including the response text.
554 Your access to this mail system has been rejected due to the sending MTA's poor
reputation. If you believe that this failure is in error, please contact the intended
recipient via alternate means.
-----
Please get in contact with the remote smtp server side admin and inform them about the Poor reputation their SMTP server have on the Sender Base network. They can also take a look on the Web page "http://www.senderbase.org" to get additional information about the Poor reputation score their server have. On the sender base web page they should also be able to find an contact address to which they have to contact so that they get further details about the issue which cause the bad score.
As a workaround so that you can get the messages from the remote side without any further sender base rejection, you can insert the IP address or hostname of the relevant Remote SMTP server side into an Allowed HAT Sender Group. With this the remote side should not get rejected again and you should be able to receive the messages from them without further issues.
Thank You!
Regards,
Mohit Soni
