Explanation:

- Networking protocol:

- SMTP is indeed a type of networking protocol, but this answer lacks specificity regarding its function.

- Protocol used for transferring message between end user and Mail Server:

- This is partly correct, but primarily SMTP is used to transfer messages between mail servers and not directly between an end user and a mail server.

- Encryption standard:

- SMTP is not an encryption standard. It deals with message transfer, not encryption.

- Protocol used for smart card message interchange:

- SMTP is not used for smart card message interchange; it is specifically for email.