Which is the default TCP port used in SMTP for non-encrypted communications?

Explanation & Hint:

The following TCP ports are used in most common email protocols:
TCP port 25: The default port used in SMTP for non-encrypted communications.
TCP port 465: The port registered by the Internet Assigned Numbers Authority (IANA) for SMTP over SSL (SMTPS).
TCP port 587: The Secure SMTP (SSMTP) protocol for encrypted communications, as defined in RFC 2487, using STARTTLS.
TCP port 110: The default port used by the POP3 protocol in non-encrypted communications.
TCP port 995: The default port used by the POP3 protocol in encrypted communications.
TCP port 143: The default port used by the IMAP protocol in non-encrypted communications.
TCP port 993: The default port used by the IMAP protocol in encrypted (SSL/TLS) communications.