Hi Vdecock,
According to your description, I have checked the domain name you provided. I haven’t found the TXT record or MX record for verify.
In general, to verify and add your custom domain to Office 365, it needs to add a TXT or MX records at your domain hosting provider. Office 365 use this created TXT or MX record to verify the ownership of your domain. Typically, it may take about 15 minutes but can take up to 72 hours for the record that you created to propagate through the DNS system.
If the DNS record can’t take effect, I suggest you ask for the help from OVH support.
For the detailed information and steps, please refer to the articles below:
For Enterprise plan:
Work with domain names and DNS records in Office 365
For Professionals and small plan:
Change name server records at a domain registrar
Thanks,
Jason Jiang