SMTP Mail Processing Enhancements - Reference Information

   Solutions for FL310

Notes:

  • The APAR solutions discussed here are implemented in the code "base" for TCP/IP Function Level 320 (and later levels of TCP/IP for VM).
  • Support for TCP/IP Function Level 310 ended on 31 March, 2002.

APAR PQ14324 for TCP/IP FL310 (available via PTF UQ27175) provides the following new statements and support that can be used to address spamming issues.

Note!
For detailed information about the support provided by APAR PQ14324 and the statements that follow, consult its on-line documentation.

  1. VerifyClient Statement - The VerifyClient statement is used to indicate to the SMTP server whether or not client verification is to be performed. Client verification can be performed using built-in VerifyClient function (VERIFYCLIENT YES, same as APAR PQ06018), or using a user exit (VERIFYCLIENT exit). The VerifyClient exit will be called for each HELO processed for a given mail item.

  2. ForwardMail Statement - The ForwardMail statement provides a mechanism to control who can use the VM system to forward mail. When SMTP determines that the addressee specified on the RCPT TO record is not on the local system, it will call the exit routine. An installation could prevent forwarding all mail through their SMTP server by simply specifying FORWARDMAIL NO. For a more granular approach you can specify FORWARDMAIL EXIT and tailor the sample exit (SMTPFWDX) to your specific needs.

  3. SourceRoutes Statement - The SourceRoutes statement provides the ability for an installation to prevent source routing through their SMTP server. When "NO" is specified the server will attempt to deliver the mail directly to the final destination (mailbox). There is no exit associated with this statement.

    Note!
    APAR PQ24183 (available via PTF UQ27423) further modifies the SourceRoutes statement support. Use this link to obtain more information about these changes.

  4. SMTPCMDS Statement - The SMTPCMDS statement provides the means for an exit to be invoked whenever certain SMTP commands (ie. MAIL, RCPT, DATA, HELO, etc.) are received by the server. The use of the SMTPCMDS exit routine requires knowledge of the SMTP Protocol for the given command that the exit is being invoked.