SMTP relay - Client host rejected: AP0002

Hello everyone,

We have to send emails to a Bouyges address (a french telecom company) and I got this back:

Sorry, no SMTP connection got far enough; most progress: RCPT TO response; remote host said: 554 5.7.1 <...dsl.sta.abo.bbox.fr>: Client host rejected: AP0002 Please use your ISP mailserver. (#5.5.0)

I searched on Google to find a way to send the emails and what I understand is that I have to configure the SMTP relay of Bouyges.

What I found are only configurations for postfix and I don't know how to configure it on an Exchange On-premise server, do you have any info?

The SMTP server of Bouyges is smtp.bbox.fr  

What I don't know if it's possible to do is to use this relay only for the bbox mails address.

Thanks for any help!