ZyXEL UAG4100 User Guide - Page 235

CHAPTER 17 SMTP Redirect 17.1 Overview SMTP redirect forwards the authenticated client's SMTP message to a SMTP server, that handles all outgoing e-mail messages. In the following example, SMTP server A is connected to the lan2 interface in the LAN2 zone. When a client connected to the lan1 interface in the LAN1 zone logs into the UAG and wants to send an e-mail, its SMTP message is redirected to SMTP server A. SMTP server A then sends it to a mail server, where the message will be delivered to the recipient. The UAG forwards SMTP traffic using TCP port 25. Figure 153 SMTP Redirect Example 17.1.1 What You Can Do in this Chapter Use the SMTP Redirect screens (see Section 17.2 on page 236) to display and edit the SMTP redirect rules. 17.1.2 What You Need to Know SMTP Simple Mail Transfer Protocol (SMTP) is the Internet's message transport standard. It controls the sending of e-mail messages between servers. E-mail clients (also called e-mail applications) then use mail server protocols such as POP (Post Office Protocol) or IMAP (Internet Message Access Protocol) to retrieve e-mail. E-mail clients also generally use SMTP to send messages to a mail UAG Series User's Guide 235