What exactly is smtp?
Simple Mail Transport Protocol (SMTP) is the standard protocol for transmitting electronic mail on top of a transport protocol such as TCP. Many e-mail systems such as Groupwise, cc:Mail, Exchange, and Lotus Notes and client software programs such as Outlook, Netscape and Eudora support and use SMTP to send and receive mail. The gateway uses SMTP to receive mail from e-mail servers and to send mail with fax confirmations and incoming faxes to your users.