How to reject/detect emails claiming to be from my own domain?

Fri Dec 23 20:00:10 UTC 2016

I use Mailscanner and Send mail.  We have a few instances that we are receiving spam from jack at example.com<mailto:jack at example.com> to jack at example.com<mailto:jack at example.com> and it is getting through.  I have not seemed to find and answers as to how to stop this? Anyone got an Idea.  We already have SPF setup which helps but is not fully for this situation.

Thank you.
Philip Parsons

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