Which protocol is commonly associated with secure email transfer?

The protocol associated with secure email transfer is SMTPS. This protocol is an extension of the standard Simple Mail Transfer Protocol (SMTP), which is used to send emails. SMTPS operates over a secure socket layer (SSL) or transport layer security (TLS), creating an encrypted connection between the email server and the client. This ensures that the data being transmitted, such as email content and attachments, remains private and secure from potential interception.

While the other protocols mentioned serve important roles in email management, they do not specifically address secure email transmission. IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol) are both primarily used for retrieving emails from a server, not for sending them. SMTP is the standard protocol for sending emails; however, without the secure layer provided by SMTPS, it lacks the encryption necessary to protect the communication during transfer, making SMTPS the preferred choice for secure email transactions.