Accept relay messages from Post Office Protocol clients

One of the options for relay restriction enables Post Office Protocol (POP) clients to relay messages through Simple Mail Transfer Protocol (SMTP) for a specified period of time after they log on to the POP server.

This function is commonly called POP before SMTP. It is particularly useful for mobile employees that use dynamic IP addresses, because security checking functions that use fixed IP addresses are not effective for checking dynamic IP addresses. You can enable a mobile employee to authenticate once to the POP server and to send e-mail for a designated period of time (15 - 65535 minutes) without authenticating again.

For example, you might configure the server to allow your remote users to relay messages through the SMTP server during a four-hour (240-minutes) period of time after they log on to the POP server. In this example, a mobile worker logs on to the POP server to retrieve his e-mail. The POP server records the user's IP address and a time stamp in a queue. An hour later, the user decides to send an e-mail message. When he sends the e-mail message using SMTP, the SMTP server checks the queue to verify that the user accessed the POP server to retrieve e-mail sometime during the configured time period. After the user is verified, the SMTP server relays the e-mail message to the SMTP client for delivery to the e-mail recipient.

Note: To more precisely control the users that can access your e-mail server, you can use the relay restriction function and the connection restriction function together. For example, you might want to restrict specific groups of users from connecting to your e-mail server but allow certain POP clients within that group to use your SMTP server to send e-mail messages.

To enable POP clients to relay messages for a specified length of time, follow these steps:

  1. In iSeries™ Navigator, expand your iSeries Server > Network > Servers > TCP/IP.
  2. Right-click SMTP and select Properties.
  3. Click the Relay Restrictions tab.
  4. For Allow relay messages, select Specified.
  5. Select From the POP client for the following duration (15 - 655535) and enter a time value to specify the number of minutes to allow a client to send mail using the SMTP server.
  6. Click Help for more information.
  7. Click OK.
Parent topic: Restrict relays