SMTP Extension
What is STARTTLS command?
STARTTLS is a command that is used by the email client to inform the email server that client wants to upgrade a insecure connection to a secure connection by using TLS or SSL.
Which port is used for encrypting the SMTP messages using STARTTLS?
Port 587 is used for encrypting the SMTP messages using STARTTLS that allows to establish a secure email connection between email client and email server.
What are the limitations of STARTTLS?
STARTTLS has a limitation that it is so-called opportunistic. The encryption can be used only if it is negotiated between the both sending and receiving servers over an unencrypted connection.
SMTP Extensions: STARTTLS, and DANE
SMTP stands for Simple Mail Transfer Protocol. SMTP is an application layer protocol. Whenever a client needs to send mail, opens a TCP connection to the SMTP server and then sends mail over the network. The connection is established by the SMTP server through port 25.