Simple Mail Transfer Protocol (SMTP) is a protocol of the internet protocol family that is used for exchanging e-mails in computer networks. It is primarily used to upload and forward e-mails. To retrieve messages, other specialised protocols are used, such as POP3 or IMAP. SMTP-servers accept traditional connections on Port 25. Newer servers also use Port 587 to receive mail from authenticated users that must then be forwarded to other mail servers. This should prevent spam.