According to that, you ultimately need to talk to John. I don't understand why you would need to send an email to "admin" rather than just send it to John, when they have given you John's email address. I would copy the text of the email to "admin", explain to them (or remind them) what the issue is, and ask them if they can do whatever needs doing.
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netePeter asked me to contact admin @ example.com and mention the code "BX73".This doesn't seem necessary. You already said it.