I have brought an ovh vps with domain name. I had disabled ip6. It gave me a headache because of blacklisting. I’ve checked the mail using mailtester and filled a form in spamhaus. I’ve also had to delete /etc/resolv.conf two or three times to make a link. May be ovh is forcing it. It was about 5 months ago, so I’m not really sure what I did, but now everything is good and I have disabled ip6 in yunohost