Hi, sys-apps/smartmontools should be referring to "mail-client/mailx" in its elog command, rather than the non-existent "virtual/mailx".
# emerge -pv virtual/mailx These are the packages that would be merged, in order: Calculating dependencies... done! [ebuild R ] mail-client/mailx-8.1.2.20050715-r1 0 kB
Sorry, I didn't spot the PROVIDE="virtual/mailx" in mail-client/mailx/mailx-8.1.2.20050715-r1.ebuild