Suspeits

The infinityfree.com emails are sent by us and the hostmessage.info emails are sent by our supplier iFastNet. We make use of Amazon SES, iFastNet uses their own email infrastructure.

As you’ve observed, both emails pass DMARC, so technically there is nothing wrong with it. But spam detection goes far beyond checking whether the listed sender allows that email to be sent, and there could be any number of reasons why your email provider decides to flag one email as spam and not the other.

All I can take away from this is that our email is being delivered correctly. The hostmessage.info emails are not critical and are not sent by us, so there is not much we can or need to do about it.