Question:
Domino and Native SMTP cannot run on the same iSeries

Answer:
Some has complained, that it is not possible to run the native SMTP server (that InterForm400 use) if you already has Domino installed on the same iSeries. The problem is, Domino uses a different SMTP server which thereby conflicts as they both need to use the same port number. The solution is to bind each SMTP server to specific IP-addresses. For more information use the links below:

http://www-1.ibm.com/servers/eserver/iseries/domino/r5smtp/r5smtp.htm
http://www-1.ibm.com/servers/eserver/iseries/domino/r5smtp/config.htm