I've looked into blacklists, but we're going to take a smarter approach to it. We'd rather let some SPAM in, to keep the flow of legit e-mail going, since I've had the fun before of having legit e-mail blocked.
Um, I hope you mean EHLO or HELO. If you require just HELO, only really old SMTP servers will be able to deliver mail.
Other than that, I have no comments. Let us know how it works out.
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