So this isn’t specifically an issue with Mautic but rather your DNS setup. Make sure that SPF, DKIM and DMARC are set up correctly for the domain that you are using to send emails. If you’re using a third-party service (like Mailgrid or SendGrid), perhaps reach out to them for assistance on setting this up with their service.
Use https://www.mail-tester.com/ to test your emails before they are sent in bulk to make sure that they will get into an inbox.
Create a contact in Mautic and use the email address that the tester tool gives you - https://www.mail-tester.com/.
Send a test email through the Mautic system and see what the results are. You can share the test results URL here. There’s no security concern with the info on the page.
According to the instructions (not great at French), you were supposed to create a cname for ‘psrp.piikla.com’ and point it to “rp.postal.piikla.com”. I don’t see that cname registered on piikla.com.
Sorry, I’m confused. LWS is where you registered your domain name yes?
Webhost and where you host your website are the same thing, in this case, your VPS Contabo. Are you also hosting your Mautic on the same VPS on Contabo?
Oui j’ai enregistré mon nom de domaine chez lws et c’est mon hebergeur web aussi y a peu de temps . Depuis que j’ai commencé mautic j’ai décidé à transferer mon domaine chez contabo( sans avoir encore configurer le NS chez LWS donc je pense que lws heberge encore mon domaine principale qui est piikla.com ) Par contre mautic est hebergé dans un vps chez contabo , ainsi que Postal smtp sous un sous domain postal.piikla.com et focus.piikla.com .