A White ipfilter is an another ipfilter file, an addition to the ipfilter feature which prevents specific IPs to be banned even if they already exists the main ipfilter.dat file.
You can create and edit this file manually in config dir.
Added by Stulle, since MorphXT v11.2
ADD: IP Filter White list [Stulle] IP Filter White List: + IPs on this list will not be banned + use "ipfilter_white.dat" to add IPs to the White List
-  eMule docs how to find the config directory