Mail Delivery System - OVH

Bonjour à tous,

J'ai un problème de boite mail depuis plusieurs moi. Lorsque je tente d'envoyer un mail (que ce soit vers Gmail ou ailleurs) je reçois cela :

This is the mail system at host mo540.mail-out.ovh.net.

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

_mail de la personne_ said:
550-5.7.26 This mail is unauthenticated, which poses a security risk to the
550-5.7.26 sender and Gmail users, and has been blocked. The sender must
**550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,**
** 550-5.7.26 DKIM checks did not pass and SPF check for [magicovaries.com]**
did 550-5.7.26 not pass with ip: [51.210.91.51]. The sender should visit
550-5.7.26 https://support.google.com/mail/answer/81126#authentication for
550 5.7.26 instructions on setting up authentication.
d2-20020adfe842000000b003141f7c1240si4495470wrn.972 - gsmtp (in reply to
end of DATA command)

Je pensais avoir déjà tout fait pour le SPF et le DKIM. Comment vérifier que tout ok ? Quelles modifications dois-je apporter ? Merci par avance pour votre aide précieuse.

Alix.