Per the IETF, you must have both POSTMASTER@, and ABUSE@, for every domain capable of sending and receiving e-mail.
If an e-mail is sent to one of those addresses, a human, of authority for the security of your MX server must respond to, and act upon, the issue. Abuse@ is important because it is commonly used to report phishing attacks and potential identity theft; eg:
[names masked in example text below to prevent spam filters, from blocking post.]
"An audit of your Ch^se (or W3lls F0rgiving" account indicates suspicious activities, and you must login, via the link below to update your information before you can continue to use your account."
When the user clicks on the link, they are usually taken to a look-alike link, usually PHP based, and they are either suckered into providing their personal information, like username and password, or bank, credit card, and other identify theft information.
When someone receives a message like this, they should IMMEDIATELY DELETE the message because no bank or credit card company will never send an e-mail with such a link.
Ideally, they will also copy the entire header and FORWARD the message, UNALTERED, with the mess header inserted prior to the original message before deleting the message and emptying their trash.
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