SMTP is at the heart of the Internet electronic mail. Although SMTP has numerous
wonderful qualities, it is nevertheless a legacy technology that posses certain archaic characteristics. For example, it restricts the body of all mail messages to simple 7-bit ASCII.
This made since when transmission capacity was scarce and no one was emailing large
attachments. But today, in the multimedia era, the 7-bit ASCII is a bit of a pain—it requires
binary multimedia data to be encoded to ASCII before being sent over SMTP; and it requires
the corresponding ASCII message to be decoded back to binary after SMTP transport.

SMTP does not normally use intermediate mail server for sending mail, even when the two
mail servers are located at opposite ends of the world. SMTP protocol has many similarities
with protocols that are used for face to face interaction. First the client SMTP has TCP
establish a connection on port 25 to the server SMTP. Once this connection is established,
the server and client perform some application-layer handshaking, (just like people
introduce themselves before transferring information. During this SMTP handshaking
phase, the SMTP client indicated the email address of the sender and the email address of
the recipient. Once the SMTP client and server have introduced themselves, the client sends
the message. SMTP can count on the reliable data transfer service of the TCP to get the
message to the server without errors.