When you check the email relayers option within WHM then it shows empty. You can try the following change on your server. Using pico or vim
pico /etc/passwd
and search for the following entry.
mailnull:x:47:47::/var/spool/mqueue:/sbin/nologin
Change it to
mailnull:x:47:12::/var/spool/mqueue:/sbin/nologin
Restart the eximstats on the server,
/scripts/restartsrv_eximstats
The email relayers should now be visible within WHM.