Disallow use of http or https link in rich text field on forms

Wanting to stop any user with a valid email address submitting their contact details on our online and inline forms by spamming or scamming our 'contact us', 'blog subscription' or 'request for informaiton' forms by adding a link using http or https web links to spam or scam sites in our 'Message' rich text forms

 

usual spam 'captcha' does not help with this

 

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