<P> Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (email) transmission . First defined by RFC 821 in 1982, it was last updated in 2008 with Extended SMTP additions by RFC 5321, which is the protocol in widespread use today . </P> <P> Although electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user - level client mail applications typically use SMTP only for sending messages to a mail server for relaying . For retrieving messages, client applications usually use either IMAP or POP3 . </P> <P> SMTP communication between mail servers uses TCP port 25 . Mail clients on the other hand, often submit the outgoing emails to a mail server on port 587 . Despite being deprecated, mail providers sometimes still permit the use of nonstandard port 465 for this purpose . </P> <P> SMTP connections secured by TLS, known as SMTPS, can be made using STARTTLS . </P>

Which type of email server is typically used for outgoing mail