Bank information (Account & Routing numbers) replaced in email

I've been in IT over 20 years and I've never seen this one before, but it seems to have actually happened.

Someone from our company emailed an external party and included a PDF attachment with our bank information, including account and routing numbers, so that the party could send us some money. When they received the email, it had no attachment, but it did have bank information *below* the signature of the original email. The bank information was to a …

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