SPF neutral after setting up a custom MAIL FROM header

After setting up a custom MAIL FROM header to mail.mydomain.com the SPF status of my emails has become neutral. When inspecting an email, I can see this:

spf=neutral (google.com: 69.169.224.2 is neither permitted nor denied by best guess record for domain of 01070183be9ac4f5-9e55550f-9eb0-465d-93a3-06902380d9f7-000000@mail.mydomain.com) smtp.mailfrom=01070183be9ac4f5-9e55550f-9eb0-465d-93a3-06902380d9f7-000000@mail.mydomain.com;

My DNS records are as follows:

• MX 10 mail.mydomain.com feedback-smtp.eu-central-1.amazonses.com
• TXT mydomain.com v=spf1 include:mx.ovh.com include:amazonses.com ~all

What can I do to be able to have a PASS mark on SPF while also using a custom MAIL FROM header?