On iSeries / AS400 servers the executables for Crossware Mail Signature are contained within the Library "XWARE".
As part of the installation process, two links are created to these programs in "/QIBM/UserData/Lotus/Notes/"
To check that these links have been created, issue the following command:
Select option 5 "Display"
This should show the "libsig" and the "esig" links