What service is provided by SMTP?

SMTP (Simple Mail Transfer Protocol) provides the service that allows clients to send email to a mail server and the servers to send email to other servers. It is a protocol used for sending emails across the Internet. SMTP is involved in the process of mail dispatch from a client’s email program to the recipient’s mail server, and also between different mail servers for relaying email.

The other options you mentioned refer to different services:

• Allowing remote access to network devices and servers: This is generally the role of protocols like Telnet or SSH (Secure Shell).
• Using encryption to provide secure remote access to network devices and servers: This describes SSH (Secure Shell).
• An application that allows real-time chatting among remote users: This refers to instant messaging services or applications, but it is not specifically tied to a single protocol or service.