Spam Confidence level 5

Hi all,

I’m hoping for your support.
We use Microsoft 365 e-mail.
In the SPF record there is ‘a’ so the domain is allowed.
Contact Form 7 e-mails are delivered in the SPAM folder.

Below the message header.
What am I doing wrong?

contoso.nl = our domain
receiverdomain.nl = the customer filling in the contact form
myserver.nl = web hosting server

Thank you!

1 Authentication-Results spf=pass (sender IP is 1.1.1.1) smtp.mailfrom=contoso.nl; receiverdomain.nl; dkim=none (message not signed) header.d=none;receiverdomain.nl; dmarc=bestguesspass action=none header.from=contoso.nl;compauth=pass reason=109
2 Received-SPF Pass (protection.outlook.com: domain of contoso.nl designates 1.1.1.1 as permitted sender) receiver=protection.outlook.com; client-ip=1.1.1.1; helo=myserver.nl;