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Apparent conflict between sendmail and SMTP over port 25

Technote (troubleshooting)


When I set up sendmail for the sole purpose of using emails as a print destination for InfoPrint IP Printway, there appears to be a conflict on port 25.

The problem I have now is that there is a conflict on port 25. The IBM Redbooks publication z/OS V1R12 Communications Server TCP/IP Implementation: Volume 2 Standard Applications (SG24-7897-00) directs the user to reserve port 25 for sendmail with the following TCP/IP PORT parameters: 25 TCP OMVS

But port 25 is already reserved for SMTP with the following TCP/IP PORT parameters: 25 TCP SMTP

Regardless of which TCPIP PORT statement is specified, SMTP and sendmail cannot be brought up at the same time because of this conflict.

Can the port for sendmail be something else instead of 25? Or, is port 25 a requirement?

Resolving the problem

InfoPrint uses sendmail client functions and not the sendmail server functions so there is no conflict with port 25. Port 25 is necessary only for the server function to open a listening port. 

You do not need to start the sendmail listening daemon. Any undeliverable emails will be handled by SMTP. Because all the error messages you are seeing describe errors running the sendmail listening daemon, those messages should go away if you do not start the sendmail listening daemon.

Document information

More support for: z/OS Communications Server

Software version: 1.11, 1.12, 1.13, 2.1, 2.2, 2.3

Operating system(s): z/OS

Reference #: 1578969

Modified date: 02 January 2014

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