I have the following SPF record:
v=spf1 include:_spf.mailspamprotection.com include:_spf.google.com ip4:209.85.220.0/24 ~all
Although I have included _spf.mailspamprotection.com in my SPF record, which includes ip4:146.66.121.0/24, I get SPF Fail from delivery.mailspamprotection.com IP:146.66.121.100. I have the same issue with the following IP addresses from delivery.mailspamprotection.com.
146.66.121.63
146.66.121.85
146.66.121.80
146.66.121.212
146.66.121.88
146.66.121.89
146.66.121.64
146.66.121.164
146.66.121.66
It is not clear what the cause of SPF Fail is.