Free.fr spam

Hi everybody !

sorry for my English…
i used disroot since november 2017, and since end of march, each time i’ll try to send a email to free.fr domain, i’ve got a spam message…apparently, free manages disroot as a spam…
My brother’s mail (disroot too) is the same…we can’t send a email to XXX@free.fr
can you help me ? disroot isn’t working any more in France if Free.fr stays like that.
thks

PS: i’ve got
Undelivered Mail Returned to Sender
This is the mail system at host disroot.org.

I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

               The mail system

xxx@free.fr: host mx1.free.fr[212.27.48.7] said: 550 spam detected (in
reply to end of DATA command)

Reporting-MTA: dns; disroot.org
X-Postfix-Queue-ID: 369AD2E61C
X-Postfix-Sender: rfc822; mome@disroot.org
Arrival-Date: Sun, 13 May 2018 10:51:52 +0200 (CEST)

Final-Recipient: rfc822; xxx@free.fr
Original-Recipient: rfc822;xxx@free.fr
Action: failed
Status: 5.0.0
Remote-MTA: dns; mx1.free.fr
Diagnostic-Code: smtp; 550 spam detected

Thanks for the report. We’ll be looking into it.

Quick check reveals we (disroot.org) IP address is not blocked at free.fr so thats a good sign.

According to: http://postmaster.free.fr/index_en.html

550 spam detected
Reason

You receive this refusal message when one mail was detected as a spam by our antispam filter and the delivery was rejected. The non delivery report has been sent by the SMTP server you have used or, if you did not send this mail, by the SMTP server who have relayed a mail spoofing your email.
Solution

If you did send the mail, you should at first check your mail to make sure it should not be missdetected as a spam, either by using an antispam softwate or by checking if the mail is syntaxically correct and if you do not use any mecanism that are known to be used by spammers.
Failing that, you may send us a sample of rejected emails by following these instructions.

and:
http://postmaster.free.fr/index_en.html#faux_positifs
It could be something wrong with your email client you use, the content of the email or something that triggers the spam checker on the side of free.fr. We need to check whether it is triggered for all the emails sent from our server or just your particular case. Let’s continue investigating and troubleshooting via our internal ticketing system. Please send email to support_at_disroot.org and if possible (to speed up the process) please add headers of the email you are trying to send, username of your brother too so we can easier troublleshoot by examining logs.

Also is there a way to obtain email account from free.fr so we could better check things on both sides?

i tried to check the ip adress and it’s ok for free
i used smtp disroot.org port 587 to send an email
i’ve got the same result with the webmail, directly from firefox