Akismet, the spam filtering plugin, used to be the only reason for this orange border, but on the
Contact Form 7 3.1 (or later versions), the error message with the orange border occurs for multiple reasons.
Contact Form 7 3.1 has introduced nonce verification for contact forms. If the verification fails, Contact Form 7 treats the form submission as spam. This can occasionally cause false-positives when using cache plugins. When an old cache file remains for longer than 24 hours, nonce verification will fail, and you’ll see an error with an orange border.
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