If you are upgrading from a 0.4.x version of ifile, you will need to return
your MH refile program to its rightful place.  Previous ifile installation
programs had renamed the MH refile program as "refile.bak" and created a
symbolic link to irefile in its place.

Also, if you are upgrading from any previous version, you will need to change
any instances of "ifilter" and "irefile" to ifilter.mh and irefile.mh.  If
you did not do any customization of ifile's installation, the only place
this will need to be changed is in your ~/.maildelivery file.