Error while sending mail to an other company

[Samuel lecoz]

Hello since one week that error persist, we check the configuration of our mail server and everything's fine. 
I think you can help us with this. We need to send mail to the domain france-boissons.fr from our (crous-rennes.fr).

server-6.tower-271.messagelabs.com #<server-6.tower-271.messagelabs.com #5.0.0 smtp;553-you are trying to use me [server-6.tower-271.messagelabs 553-.com] as a relay, but I have not been configured to let 553-you [194.254.122.180, edge2.crous-rennes.fr] do this. 553-Please visit www.symanteccloud.com/troubleshooting for 553-more details about this error message and instructions 553 to resolve this issue. (#5.7.1)> #SMTP#

Please ask for any needed informations.

Thanks !

[Samuel lecoz]

hi, 

We really need you're assistance. Since 2 week we cannot command anything from France-boissons. if you need more information you can contact us by mail or by responding here. Thank you for you're future assistance.