How does one rollback to a previous rpm? I must confess I have forgotten.
I always run "rpm --help" to remember. The switch you want is --oldpackage. It tells RPM that it's acceptable to "update" to a package with a lower version/release number.
I tar up /etc/mail and the random sendmail config files not yet moved there (eg. aliases and smrsh) before doing an upgrade. I then unpack it to /tmp and diff it to the upgrade aftermath to see what it changed. Usually it's harmless but this sounds like a case where the practice will be valuable.