What is one consequence of an Unauthorized IP Address in email delivery?

One consequence of an unauthorized IP address in email delivery is that the email may be bounced back. This occurs because the receiving mail server checks the sender’s IP address to confirm whether it is legitimate and authorized to send emails on behalf of the domain. If the IP address does not match the expected or authorized addresses, the receiving server may reject the email outright, leading to a bounce-back. This process is a critical part of maintaining email security and integrity to prevent spam, phishing, or spoofing attacks.

The other possible outcomes, such as delivery with spam markings or delays, may occur under different circumstances but are less directly tied to the concept of unauthorized IP addresses specifically leading to rejection.