SPF (Sender Policy Framework) is used by Microsoft 365 to filter incoming messages. And once you are using Microsoft 365, you already have included something like spf.protection.outlook.com to your domain records. The record confirms that Microsoft can send messages on your behalf.
And since Xink ReRouter servers push messages back to Microsoft 365 after processing, they should be allowed to do it smoothly. So, if you are experiencing any false positive spam detection issues, add the following statement to your domain(s) SPF record:
So the whole record would look like this:
"v=spf1 mx include:spf.protection.outlook.com include:spfrerouting.xink.io ~all"
Please note that spfrerouting.xink.io includes a soft fail option, if it is not acceptable in your case, add our IP addresses directly.
Here is the list of Xink relay IP addresses by data center:
Sample record for US data center:
"v=spf1 mx include:spf.protection.outlook.com ip4:188.8.131.52 -all"