We put two notices on our site - both are in the footer so they appear on each page. Notice 1 talks about phishing, notice 2 reminds them that our e-mail links are not secure and should not be used for sensitive information. We ran both by our auditors and they said we could phrase it however we wanted to (wish I had that on tape . . . an auditor saying, "whatever, it's OK.")
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If you approach life with pure logic you can avoid almost all of the fun.