TCP/IP SMTP User Exits Support APAR PQ14324 VM TCP/IP ... - IBM

More documents

Recommendations

Info

RCPT TO:Background 6
Client Verification ExitIt is sometimes desirable to provide some indication that the host sending or forwarding a piece of mailcorresponds to the IP address assigned to the client host. The client verification exit can be used todetermine if a client host name and IP address match, and to include the result of that determination in themail headers. The VERIFYCLIENT statement in the SMTP configuration file allows you to specify whetheran exit will be called, or if verification will be done via the built-in client verification function.When used, the client verification exit is called for each HELO command processed for each mail itemreceived from the network; client verification is not performed for mail items received from the SMTPreader.The changes associated with this exit add the following configuration statements, commands, andsamples: VERIFYCLIENT statement for the SMTP configuration file (SMTP CONFIG) SMSG VERIFYCLIENT command REXX and assembler sample exits.This exit can be used to perform the following function, plus others you may deem useful in yourenvironment: Reject mail from a particular host. Mark certain trusted sites as verified, but perform verification on all others. Control which users use a particular SMTP server.Built-in Client Verification FunctionThe built-in client verification function of the SMTP server can be used to determine if a client host nameand client IP address match, and to include the result of that determination in the mail headers. Thisfunction will perform a DNS lookup against client-provided HELO command data, and will then insert amessage into the mail header that reflects the result of this lookup.Client verification performed using the built-in function has three possible outcomes:SuccessFailureThe data the client provided in the HELO command corresponds to the client address. Thefollowing line is inserted into the mail header:X-Comment: localhost: Mail was sent by hostThe data the client provided in the HELO command is not associated with the client IPaddress. In this case, a reverse name lookup is done against the client IP address todetermine the actual host name. The following line is inserted into the mail header:X-Comment: localhost: Host host claimed to be helodataUnknown The validation could not be performed. This situation could occur if the name server is notresponding, or the verification could not be performed in the allotted time (as controlled bythe VERIFYCLIENTDELAY statement). The following line is inserted into the mail header:X-Warning: localhost: Could not confirm that host [ipaddr] is helodataThe terms used in the previously listed mail header messages are described in more detail here:localhosthelodatathe local VM host namethe data the client provided with the HELO commandClient Verification Exit 7
Page 1 and 2: IBM®TCP/IP SMTP User Exits Support
Page 3 and 4: BackgroundAs the use of e-mail has
Page 5 and 6: ►►──QUIT──────
Page 7: SMTP Commands ExitIn addition to th
Page 11 and 12: When this entry is processed, the f
Page 13 and 14: Because an identical exit parameter
Page 15 and 16: ASSEMBLER Parameter ListNote: Gener
Page 17 and 18: Table 4. Client Verification Exit R
Page 19 and 20: EXITIndicates a mail forwarding exi
Page 21 and 22: Table 5. Mail Forwarding Exit - Sam
Page 23 and 24: ASSEMBLER Parameter ListNote: Gener
Page 25 and 26: User Word 1Provided for use by the
Page 27 and 28: SMTP Commands ExitThe SMTP server c
Page 29 and 30: EXPNIndicates the exit routine is t
Page 31 and 32: VRFYIndicates the exit routine is t
Page 33 and 34: REXX Parameter ListInputsTable 10.
Page 35 and 36: Port number of clientIf the connect
Page 37 and 38: Table 12. SMTP Commands Exit Return
Page 39: ►►──SMSG──server_id─

TCP/IP SMTP User Exits Support APAR PQ14324 VM TCP/IP ... - IBM

Create successful ePaper yourself

Delete template?

Save as template?