Email does not make it to my recipient

I have always had problems with my clients not receiving my emails.  Finally one of my clients sent me a report of why my email ended up in their quarantine folder.

The report showed IP address, Location, recipient, inbound, message ID, Etc.

But it also has stuff I don't understand:

DMARC:  Pass

DKIM: Test

SPF: Fail

Composite authentication: Pass

I am assuming that the SPF failing is the reason.  Can I get some help to get this fixed?