Exam CS0-002 topic 1 question 234 discussion

It's A.... SPF (Sender Policy Framework) is a security measure that is used to prevent email spoofing. It works by comparing the sender's IP address to a list of authorized IP addresses that are published in the sender's DNS records. If the IP address does not match the authorized list, the receiving mail server will reject the message with an error 550.

SPF is failing. SMTP Error 550 An email error code indicates an unsuccessful email transaction between the sender and the recipient’s server. SMTP error 550 is one of such errors that suggests your recipient’s server bounced your incoming message.

SPF is failing means that SPF is "not" instructing the recipient server on what to do if the sender IP doesn't match the list of authorized IP addresses, therefore, D? We try not to read into these questions, but CompT doesn't make it easy.

A. 550 Blocked error or 550 Requested action not taken: mailbox unavailable is an SMTP (Simple Mail Transfer Protocol) error code. Put simply, this message means that the email you sent was blocked by the recipient's email hosting server, and returned to you. SPF is a standard email authentication method. SPF helps protect your domain against spoofing, and helps prevent your outgoing messages from being marked as spam by receiving servers. SPF specifies the mail servers that are allowed to send email for your domain.

D - port 25 is for SMTP - sending e-mail