An IT technician notices that a set of emails sent from the company's newly installed and updated mail server are not being delivered. The mail server is configured to send emails over port 25. Which of the following is the most likely cause of the issue?
A firewall is blocking port 25.
Port 25 is not designed for transferring emails with attachments.
The SMTP server should use port 143 instead.
The mail server requires an update to handle current SMTP security standards.